SCIENTIFIC ERIC. INSE£T METAMORPHOSIS FIFTY £ENTS �/950 75 © 1950 SCIENTIFIC AMERICAN, INC CENTS OUTSIDE THE AMERICAS fir:st'" in the, water! SPRING'S HERE-and it's down to the sea in boats for thousands of sailors. But first in the water-and last out for repairs-are the new LAMINAe" Resin (Fiberglas mat reinforced) motor and sail boats. These sturdy craft need no conditioning-no caulking or painting-even after a winter in the open. They will not crack, warp, rot or corrode and are highly resistant to salt water and marine worms. Light in weight, easy to launch and handle, they are always seaworthy. LAMINAe Resin, from which these boats are made, is an interesting new plastic material developed by American Cyanamid Company. Impregnated in sheets of fabric, paper or glass fiber, LAMINAe also makes possible the production of almost indestructible articles such as housings, trays, tabletops, tote boxes, lampshades, toys, electrical parts, decorative wall panels and other large parts. It is another development in Cyanamid's line of plastics that adds value to the things you buy. 'Reg. U. S. Pat. og. • AMERICAN Photo by Paul Kendall � COMPANY 30 ROCKEFELLER PLAZA, NEW YORK 20, N. Y. Materials jOl' tlte Plastics Industry-olle oj the many illdustries served by Cyanamid © 1950 SCIENTIFIC AMERICAN, INC J New Duo-Cone loudspeaker, developed at RCA Laboratories, achieves the illusion of Uliving presence/' For years, working toward the ultimate in sound reproduction, scientists have sought for living presence-the illusion that a real musician or speaker is talking, singing, playing in your home. Now, with RCA's Duo-Cone loudspeaker, the goal is achieved. Two sound-cones in acoustical ali gnment reproduce sound without distortion, and give you every tonal value from a frequency of 30 on to 15,000 ... and even 18,000 cycles. It is in most of the all-important "overtones" lie. RCA's Duo-Cone loudspeaker faithfully re­ produces every overtone-to the very peak of a violin's range-and just as faithfully gives you the deep low notes of a bass drum! In addition, the RCA Duo-Cone loudspeak­ er's wide angle of sound pervades every comer of a room without sharply directed blast or blare. Its response to tones of every frequency is smooth, flowing, and even. Ideal for monitoring radio-AM-FM See the newest advances of radio, television, and electronics at RCA Exhibition Hall, 36 vv. the area above a frequency of 4,000-seldom 49th St., New York. Admission is free. Radio touched by conventional speake�'s - that Corporation of America, Radio City, N. Y. television programs - RCA's Duo­ Cone loudspeaker gets, and passes, its toughest tests from engineers and experts in sound reproduction I RADIO eORPORA'I'ION oF AMERleA World Leader in 'Rae/lo © 1950 SCIENTIFIC AMERICAN, INC - FIrST in 7elevision LETTERS Sirs; Our article on topology in the January issue brought responses which were in­ teresting to us and which we thought might interest you. The most gratifying responses were those showing that the article had stimu­ lated scientific thought in fields outside mathematics. In a midwestern university a biologist who was working on the "lock and key" idea of protein molecule growth read the article and decided that he was faced with a topological problem. He had not realized before that there was such a branch of mathematics. He con­ sulted his colleagues in the mathematics department, and moved a long way ahead in his investigation. A chemist wrote that the article "strikes a chord with a problem I have in organic chemistry," and asked for technical references. In another letter an engineer in the Bonneville Power Ad­ minish·ation said, "We are greatly inter­ ested in new uses of topology as applied to networks [and would bel grateful for references you could give us." We would like to refer other readers with a serious interest in the subject to the book Intro­ to Topology by Solomon Lefare pleased with these responses they show the usefulness of mt'''r',,'i,�nl'p publication. our article we warned readers against trying to turn real inner tubes inside out. One reader, Mr. Bradford B. Underhill, an engineer in Collingswood, N. J., would not be deterred. He cut a three-inch 'diameter hole in 'an inner tube, turned it inside out, and sent it to us in the mail. The "grain" of the tube reversed its direction as we said it would, so experiment confirms theory. Mr. Un­ derhill says that turning an inner tube inside out "is not at all difficult if one inserts his entire arm through the hole and grabs the far side and pulls. Be care­ ful of your fingernails, however, for it is rather easy to bend them backward, with considerable pain." The inside-out inner tube is now in the mathematical museum of Fine Hall at Princeton. We have received several requests for Klein bottles. The Klein' bottle pictured on the January cover was made by Mr. 2 © 1950 SCIENTIFIC AMERICAN, INC Lee Harris, expert glass blower in Prince­ ton's Palmer Physical Laboratory, and is itself a work of art. We would also like to elucidate a point that was implied in the figures but not elaborated in the article. The four-color problem becomes a network problem when each state is given a capital and the capitals of two states with a common border are joined by a raih'oad that crosses that border only. Then one has to find a color scheme for the capitals so that capitals joined by a railroad have different colors. The railroads connecting the six capitals, etc., in the six-color map on page 23 also show how six pOints can be completely interconnected on a trans­ parent Moebius band. Also, at the top center of page 24, "opposite" means "diametrically opposite" or "centrally symmetric." HERBERT S. BAILEY, JR. ALBERT W. TUCKER Princeton University Princeton, N. J. Sirs: Claude E. Shannon's "A Chess-Play­ ing Machine" in your February number may seem a little out of focus to those who are fair-to-middling chess players but poor mathematicians. Perhaps the catch lies in Shannon's phrase, "Assuming that a suitable meth­ od of position evaluation has been de­ cided upon . . . " Now if a single method of position evaluation could be agreed Scientific American, April, 1950; Vol. 182, No. 4. 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VIRGINIA SMELTING COMPANY, West Norfolk, Virginia. upon by all chess masters, the difference between the modes of "thinking" of a human player and of a machine would probably be slight. Suppose we look at the problem from the pOint of view of pitting two machines against each other. If each of the ma­ chines were given the same method of position evaluation, what would decide the outcome of a match between them? Chance? Then if two opposing groups of mathematicians were given unlimited facilities for attempting to improve the machines on a competitive basis, what would be the method of choice? Simply to make the machines more elaborate until they had enough sections working independently to run down the 10120 variations in the average game? Or would the mathematicians rather strive to improve the validity of the numbers used in position evaluation? From the chess player's pOint of view it is the latter activity that is of interest. The fact that two grand masters, taken at random, have a good chance of dis­ agreeing on the evaluation of a position is what makes chess an interesting game. If they generally agreed on the evalua­ tion of positions, the game would then become a mere exercise in calculation. Actually, of course, we should prob­ ably invent a new game' at that point. The late Jose Raoul Capablanca, the nearest approach to a chess playing ma­ chine in the flesh yet seen, suggested in the 1920s, after he had gone undefeated for a number of years, that chess was worked out and should be modified or replaced. Capablanca's partisans in the chess world held that he would have gone undefeated forever if extraneous factors had not interfered with the work­ ing of his "flawless" mind. But others held that he fell from the championship because methods of evaluating positions that were an improvement over his own were developed. It may be suggested that there is an optimum range for a game of percep­ tion and calculation somewhere between ticktacktoe, which most of us probably remember having proved to be always drawn with best play, and games whicb are so complicated that no satisfactory method of evaluating plays can be sug­ gested. Checkers has less appeal than chess simply because it is too near the mere calculation side of this scale, and calls for too much memory work. Poker with too many wild cards is too far on the random variation side of the scale and so is less attractive than a straight game. If the machine designers really want a challenge, why don't they design a machine that will exhaust "Go," the oriental game played on the intersec­ tions of 19 lines with about 150 pieces on each side? WILLIAM NEWBERRY Alton, Ill. 4 © 1950 SCIENTIFIC AMERICAN, INC ERE the most dramatic devel­ H opment, the most revolutionary IS invention in the history of dictating machines! It's Dictaphone Corporation's some resurfacing of used records_ The TIME-MASTER is an invalu­ able aid to people who work with their minds_ Scientific Americans now have in the TIME-MASTER the newly developed recording medium, simplest, easiest and fastest means record, the amazing of making reports, recording data, the Memobelt plastic belt that heralds a whole new preparing papers and keeping up era of dictating speed, economy and with correspondence. Always ready convenience_ It is the Memobelt to listen, the alone which has made possible the first truly streamlined dictating machine, the desk-size, super-efficient Dictaphone TIME-MASTER! The Memobelt is the first and only ONE-TIME dictating medium, so in­ expensive t9 use that after tran­ scribing, simply file it or throw it away! There is 110 records TIME-MASTER clearl y anything you want to get on paper. Only by seeing the Dictaphone TIME-MASTER Mel1lobelt wi th i t s amazing can you fully appreciate i t s unequalled convenience and economy_ Call your local Dictaphone representative for a free demonstra­ tion in your own office, or . . costly, troubleSend for your free copy of "Does Your Dictating Date You?" r-----I DICTAPHONE CORPORATION Only Dictaphone Corporation makes Dicl X2 and Xa in a three dimen­ sional coordinate system, at the time X4, it spreads as a spherical wave and reaches a neighboring point (Xl+dXl, x2+dx2, xa+dxa) at the time x4+dx4' Introducing the velocity of light, c, we write the expression: vdxl� +dx22 + dX3:!= cdx4 This can also be written in the form: This expression represents an objec­ tive relation between neighboring space­ time points in four dimensions, and it holds for all inertial systems, provided the coordinate transformations are re­ stricted to those of special relativity. T4e relation loses this form, however, if ar­ bitrary continuous transformations of the coordinates are admitted in accordance with the principle of general relativity. The relation then assumes the more gen­ eral form: :t gik dXj 'dxk = 0 Ik The gil, are certain functions of the coor- 15 © 1950 SCIENTIFIC AMERICAN, INC dinates which transform in a definite way if a continuous coordinate transfor­ mation is applied. According to the prin­ ciple of equivalence, these gik functions describe a particular kind of gravita­ tional field: a field which can be ob­ tained by transformation of "field-free" space. The gik satisfy a particular law of transformation. Mathematically speak­ ing, they are the components of a "tensor" with a property of symmetry which is preserved in all transforma­ tions; the symmetrical property is ex­ pressed as follows: gik= gki The idea suggests itself: May we not ascribe objective meaning to such a sym­ metrical tensor, even though the field cannot be obtained from the empty space of special relativity by a mere coordinate transformation? Although we cannot expect that such a symmetrical tensor will describe the most general field, it may well describe the particular case of the "pure gravitational field." Thus it is . evident what kind of field, at least for a special case, general relativity has to postulate: a symmetrical tensor field. Hence only the second question is left: What kind of general covariant field law can be postulated for a sym­ metrical tensor field? This question has not been difficult to answer in our time, since the necessary mathematical conceptions were already at hand in the form of the metric theory of surfaces, created a century ago by Gauss and extended by Riemann to manifolds of an arbitrary number of di­ mensions. The result of this purely for­ mal investigation has been amazing in many respects. The differential equa­ tions which can be postulated as field law for gik cannot be of lower than sec­ ond order, i.e., they must at least contain the second derivatives of the gik with respect to the coordinates. Assuming that no higher than second derivatives appear in the field law, it is mathematically de­ termined by the principle of general relativity. The system of equations can be written in the form: Rik=O The Rik transform in the same manner as the gik> i.e., they too form a symmetri­ cal tensor. These differential equations com­ pletely replace the Newtonian theory of the motion of celestial bodies provided the masses are represented as singulari­ ties of the field. In other words, they contain the law of force as well as the law of motion while eliminating "inertial systems." The fact that the masses appear as singularities indicates that these masses themselves cannot be explained by sym­ metrical gik fields, or "gravitational fields." Not even the fact that only posi­ tive gravitating masses exist can be de­ duced from this theory. Evidently a com­ plete relativistic field theory must be based on a field of more complex nature, that is, a generalization of the symmetri­ cal tensor field. EFORE consider­ ing such a gener­ alization, two re­ marks pertaining to gravitational theory are essen­ tial for the expla­ nation to follow. The first obser­ vation is that the principle of general relativity imposes exceedingly strong re­ strictions on the theoretical possibilities. Without this restrictive principle it would be practically impossible for any­ body to hit on the gravitational equa­ tions, not even by using the principle of special relativity, even though one knows that the field has to be described by a symmetrical tensor. No amount of collection of facts could lead to these equations unless the principle of general relativity were used. This is the reason why all attempts to obtain a deeper knowledge of the foundations of physics seem doomed to me unless the basic con­ cepts are in accordance with general relativity from the beginning. This situa­ tion makes it difficult to use our empiri­ cal knowledge, however comprehensive, in looking for the fundamental concepts and relations of physics, and it forces us to apply free speculation to a much greater extent than is presently assumed by most physicists. I do not see any rea­ son to assume that the heuristic signifi­ cance of the principle of general relativ­ ity is restricted to gravitation and that the rest of physics can be dealt with separately on the basis of special rela­ tivity, with the hope that later on the whole may be fitted consistently into a generai relativistic scheme. I do not think that such an attitude, although his­ torically understandable, can be objec­ tively justified. The comparative small­ ness of what we know today as gravita­ tional effects is not a conclusive reason for ignoring the principle of general rela­ tivity in theoretical investigations of a fundamental character. In other words, I do not believe that it is justifiable to ask: What would physics look like with­ out gravitation? The second pOint we must note is that the equations of gravitation are 10 differ­ ential equations for the 10 components of the symmetrical tensor gik. In the case of a non-general relativistic theory, a system is ordinarily not overdetermined if the number of equations is equal to the number of unknown functions. The manifold of solutions is such that within the general solution a certain number of functions of three variables can be chosen arbitrarily. For a general rela­ tivistic theory this cannot be expected as a matter of course. Free choice with respect to the coordinate system implies that out of the 10 functions of a solu­ tion, or components of the field, four can be made to assume prescribed values .• by a suitable choice of the coordinate system. In other words, the prinCiple of general relativity implies that the number of functions to be determined by differential equations is not 10 but 10-4=6. ·For these six functions only six independent differential equations may be postulated. Only six out of the 10 differential equations of the gravitation­ al field ought to be independent of each other, while the remaining four must be connected to those six by means of four relations (identities). And indeed there exist among the left-hand sides, Rik, of the 10 gravitational equations four identities- "Bianchi's identities"-which assure their "compatibility. " In a case like this-when the number of field variables is equi\l to the number of differential equations-compatibility is always assured if the equations can be obtained from a variational principle. This is indeed the case for the gravita­ tional equations. However, the 10 differential equa­ tions cannot be entirely replaced by six. The system of equations is indeed "over­ determined," but due to the existence of the identities it is overdetermined in such a way that its compatibility is not lost, i.e., the manifold of solutions is not critically restricted. The fact that the equations of gravitation imply the law of motion for the masses is intimately connected with this (permissible) over­ determination. After this preparation it is now easy to understand the nature of the present in­ vestigation without entering into the de­ tails of its mathematics. The problem is to set up a relativistic theory for the total field. The most important clue to its solution is that there exists already the solution for the special case of the pure gravitational field. The theory we are looking for must therefore be a generalization of the theory of the gravi­ tational field. The first question is: What is the natural generalization of the sym­ metrical tensor field? This question cannot be answered by itself, but only in connection with the other question: What generalization of the field is going to provide the most natural theoretical system? The answer on which the theory under discussion is based is that the symmeh·ical tensor field must be replaced by a non-symmetrical one. This means that the condition gik= gki for the field components must be dropped. In that case the field has 16 instead of 10 independent components. There remains the task of setting up the relativistic differential equations for a non-symmetrical tensor field. In the attempt to solve this problem one meets with a difficulty which does not arise in the case of the symmetrical field. The principle of general relativity does not suffice to determine completely the field equations, mainly because the transfor­ mation law of the symmetrical part of the field alone does not involve the com­ ponents of the antisymmetrical part or 16 © 1950 SCIENTIFIC AMERICAN, INC - vice versa. Probably this is the reason why this kind of generalization of the field has hardly ever been tried before. The combination of the two parts of the field can only be shown to be a natural procedure if in the formalism of the theory only the total field plays a role, and not the symmetrical and antisym­ meh'ical parts separately. It turned out that this requirement can indeed be satisfied in a natural way. But even this requirement, together with the principle of general relativity, is still not sufficient to determine uniquely the field equations. Let us remember that the system of equations must satisfy a further condition: the equations must be c�mpatible. It has been mentioned above that this condition is satisfied if the equations can be derived from a vari­ ational principle. This has indeed been achieved, al­ though not in so natural a way as in the case of the symmetrical field. It has been disturbing to find that it can be achieved in two different ways. These variational principles furnished two systems of equations-let us denote them by El and E2-which were different from each other (although only slightly so), each of them exhibiting specific imperfec­ tions. Consequently even the condition of compatibility was insufficient to de­ termine the system of equations unique­ ly. It was, in fact, the formal defects of the systems El and E2 that indicated a possible way out. There exists a third system of equations, Eg, which is free of the formal defects of the systems E] and E2 and represents a combination of them in the sense that every solution of Eg is a solution of El as well as of Eo. This suggests that Ea may be the syste]� we have been looking for. Why not pos­ tulate Eg, then, as the system of equa­ tions? Such a procedure is not justified without further analysis, since the com­ patibility of El and that of E2 do not imply compatibility of the stronger sys­ tem E3, where the number of equations exceeds the number of field components by four. An independent consideration shows that irrespective of the questioJ.l of com­ patibility the stronger system, Eg, is the only really natural generali-zation of the equations of gravitation. But Eg is not a compatible system in the same sense as are the systems El and E2, whosj'l compatibility is assured by a. sufficient number of identities, which means that every field that satisfies the equations for a definite value of the time has a continuous extension representing a solution in four-dimensional space. The system Eg, however, is not extensible in the same way. Using the language of classical mechanics we might say: In the case of the system Eg the "initial condi­ tion" cannot be freely chosen. What real­ ly matters is the answer to the question: Is the manifold of solutions for the sys­ tem Eg as extensive as must be required for a physical theory? This purely mathe­ matical problem is as yet unsolved. The skeptic will say: "It may well be h'ue that this system of equations is rea­ ,sonable from a logical standpoint. But this does not prove that it corresponds to nature." You are right, dear skeptic. Experience alone can decide on truth. Yet we have achieved something if we have succeeded in formulating a mean­ ingful and precise question. Affirmation or refutation will not be easy, in spite of an abundance of known empirical facts. The derivation, from the equa­ tions, of conclusions which can be con­ fronted with experience will require painstaking efforts ancl probably new mathematical methods. 17 • © 1950 SCIENTIFIC AMERICAN, INC The Hydrogen Bomb: II In which the technical and strategic discllssion of last lssue lS continued, and a proposal lS made for a .first step toward the international control of atolnic weapons by Hans A. Bethe month Louis N. Ridenour pub­ T ASTlished an article on thc hydrogen L bomb in this magazine. The dis­ cussion is continued in this second arti­ cle because of the tremendous impor­ tance of the issue. Ridenour described the essential parts of the theory of the nuclear reactions in the hydrogen bomb, and also discussed the likely effects of the bomb on our military security. I agree entirely with his view that the crc­ ation of the H-bomb makes our country more vulnerable rather than more se­ cure. It remains for me to discuss two things: On the technical side, I shall try to clarify the many misconceptions that have crept into the discussions of the H-bomb in the daily press. On the po­ litical side, I wish to take up the moral issue and the meaning of the bomb in the general framework of our foreign rela­ tions. Everybody who talks about atomic energy knows Albert Einstein's eCllJation E=Mc": vi::., the energy release in a nu­ clear reaction can be calculated from the decrease in mass. In the fission of the uranium nucleus, one tenth of one per cent of the mass is converted into energy; in the fusion of four hydrogen nuclei to form helium, seven tenths of one per cent is so converted. ''''hen these statements are made in newspaper re­ ports, it is usually implied that there ought to be some way in which all the mass of a nucleus could be converted into energy, and that we are merely waiting for technical developments to make this practical. Needless to say, this is wrong. Physics is sufficiently far de- veloped to statc that there will never be a way to make a proton or a neutron or any other nucleus simply disappear and convert its entire mass into energy. It is true that there are processes by which various smaller particles-positive and negative electrons and mesons-are an­ nihilated, but all these phenomena in­ volve at least one particle which does not normally occur in nature and therefore must first be created, and this creation process consumes as much energy as is afterwards liberated. All the nuclear processes from which EDITOR'S NOTE The author is responsible only for the statements that appear in the text of this article. The illustrations and the captions that accompany them were pre­ pared by the editors. The infor­ mation contained in the illustra­ tions was compiled on the basis of previously published material. energy can be obtained involve the re­ arrangement of protons,and neutrons in nuclei, the protons and neutrons them­ selves remaining intact. Hundreds of experimental investigations through the last 30 years have taught us how much energy can be liberated in each trans­ formation, whether by the fission of heavy nuclei or the fusion of light ones. In the case of fusion, only the combina­ tion of the very lightest nuclei can re­ lease very large amounts of energy. 18 • © 1950 SCIENTIFIC AMERICAN, INC vVhen four hydrogen nuclei fuse to form helium, .7 per cent of the mass is trans­ formed into energy. But if four helium nuclei were fused into oxygen, the mass would decrease by only .1 per cent; and the fusion of two silicon atoms, if it ever could occur, would release less than .02 per cent of the mass. Thus there is no prospect of using elements of medium atomic weight for the release of nuclear energy, even in theory. HE main problem in the release of T nuclear energy in those cases that we can consider seriouslv is not the amount of energv released- this is always large enough-but whether there is a mecha­ nism by which the release can take place at a sufficient rate. This consideration is almost invariably ignored by science re­ porters, who seem to be incurably fas­ cinated bv E=Mc". In fusion the rate of reaction is governed bv entirely different factors from those in fission. Fission takes place when a nucleus of uranium or plu­ tonium captures a neutron. Because the neutron has no electric charge and is not repelled bv the nucleus. temperature has no important influence on the fission re­ action; no matter how slow the neutron, it can enter a uranium nucleus and cause fission. In fusion reactions, on the other hand. two nuclei, both with positive elec­ tric charges, must come into contact. To overcome their strong mutual electrical repulsiOll, the nuclei must move at each other with great speed. Ridenour ex­ plained how this is achieyed in the lab­ oratory by giving verv high velocities to a few nuclei. Tilis method is very ineffi- cient because it is highly unlikely that one of the fast projectiles will hit a target nucleus before it is slowed down by the many collisions with the electrons also present in the atoms of the target. There­ fore the energy released by nuclear reac­ tions in these laboratory experiments is always much less than the energy in­ vested in accelerating the particles. The only known way that energy can be extracted from light nuclei by fusion is by thermonuclear reactions, i.e., those which proceed at exceedingly high tem­ peratures. The prime example of such re­ actions occurs in the interior of stars, where temperatures are of the order of 20 million degrees Centigrade. At this temperature the average energy of an atom is still only 1,700 electron volts­ much less than the energies given to nu­ clear particles in "atom smashers." But all the particles present-nuclei and elec­ trons-have high kinetic energy, so they are not slowed down by colliding with one another. They will keep their high speeds. Nevertheless, in spite of the high temperature, the nuclear reactions in stars proceed at an extremely slow rate; only one per cent of the hydrogen in the sun is transformed into helium in a bil­ lion years. Indeed, it would be catastro­ phic for the star if the reaction went much faster. The temperature at the center of a star is kept high and very nearly con­ stant by an interplay of a number of physical forces. The radiation produced by nuclear reactions in the interior can escape from the star only with great dif­ ficulty. It proceeds to the surface not in a straight line but by a complicated, zig­ zag route, since it is constantly absorbed by atoms and re-emitted in new direc­ tions. It is this slow escape of radiation that maintains the high interior tempera­ ture, which in turn maintains the ther­ monuclear reactions. Only a star large enough to hold its radiations for a long time can produce significant amounts of energy. The sun's radiation, for example, takes about 10,000 years to escape. A star weighing one tenth as much as the sun would produce so little energy that it would not be visible, and the largest planet, Jupiter, is already so small that it could not maintain nuclear reactions at all. This rules out the possibility that the earth's atmosphere, or the ocean, or the earth's crust, could be set "on fire" by a hydrogen superbomb and the earth thus be converted into a star. Be­ cause of the small mass of the bomb, it would heat only a small volume of the earth or its atmosphere, and even if nuclear-FeaCtions were started, radia­ tion would carry away the nuclear energy BLAST EFFECT of present and proposed atomic weapons is projected on a map of New York City and the surrounding area. A uranium bomb set off above the SCIENTIFIC AMERICAN office in midtown would cause se­ vere destruction within a radius of a mile (small circle) ; a hydrogen bomb 1,000 times more powerful would cause severe destruction within 10 miles (large circle). much faster than it developed, and the temperature would drop rapidly so that the nuclear reaction would soon stop. H thermonuclear reactions are to be initiated on earth, one must take into consideration that any nuclear energy released will be carried away rapidly by radiation, so that it will not be possible to keep the temperature high for a long time. Therefore, if the reaction is to pro­ ceed at all, it must proceed very quickly. Reaction times of billions of years, like those in the sun, would never lead to an appreciable energy release; we must think rather in terms of millionths of a second. On the other hand, on earth we have a choice of materials: whereas the stellar reactions can use only the ele­ ments that happen to be abundant in stars, notably ordinary hydrogen, we can choose any elements we like for our thermonuclear reactions. We shall ob­ viously choose those with the highest reaction rates. The reaction rate depends first of all, and extremely sensitively, on the product of the charges of the reacting nuclei; the smaller this product, the higher the re­ action rate. The highest rates will there­ fore be obtainable from a reaction be­ tween two hydrogen nuclei, because hy­ drogen has the smallest possible charge -one unit. (The principal reactions in FLASH EFFECT of a hydrogen b omb 1,000 times more powerful than present bombs would be relatively great­ er than its blast effect. The Hiroshima bomb caused fatal burns at distances up to 4,000 to 5,000 feet (small circle). A hydrogen bomb would cause fatal burns at distances of 20 miles or more (large circle) . The inhabi­ tants of Chicago and its suburbs could thus be wiped out. 19 © 1950 SCIENTIFIC AMERICAN, INC H'+H' - H2+e+ • + • - �+ . H2+ H' - He3+ hv 1.4 mev 5 mev �+. - �+� H3+ H' - He4+ hv �+. - �+� H2+ H2 - He3+n �+� - 20 mev 3.2 mev �+o H2+ H2 - H3 + H' 4mev 100,000,000,000 years .5 second .05 second .00003 second .00003 second �+�-�+. H3+ H2 - He4+ n 17 mev �+�-�+o H3+ H3 -He4+ n +n 11 mev .0000012 second ? • �+�-13+0+0 THE NUCLEAR REACTIONS involving the three isotopes of hydrogen, HI, H2 (deuterium) and H3 (tritium) illustrate a fundamental consideration in making a hydrogen bomb. The reactions are at left, the energy released by each is in center, the time required for each is at right. The reactions in· volving the heavier isotopes of hydrogen proceed at a much faster rate. stars are between carbon, of charge six, and hydrogen.) We can choose any of the three hydrogen isotopes, of atomic weight one (proton), two (deuteron) or three (triton). These isotopes undergo different types of nuclear reactions, and the reactions occur at different rates. The fusion of two protons is called the proton-proton reaction. It has long been known that 'this reaction is exceedingly slow. As Robert E. Marshak stated in his article, "The Energy of Stars," in the January issue of this magazine, the pro­ ton-proton reaction takes 100 billion years to occur at the center of the sun. Ridenour pointed out that the situation is quite different for the reactions using only the heavy isotopes of hydrogen: the deuteron and triton. A number of reported measurements by nuclear physicists have shown that the reac­ tion rates for this type of fusion are high. A further variable governing the rate of the reaction is the density of the ma­ terial. The more atoms there are per unit volume, the higher the probability for nuclear collisions. It is also well known, as Ridenour noted, that the reactions would require enormous temperatures. Whether the temperature necessary to heat heavy hy­ drogen sufficiently to start a thermonu­ clear reaction can be achieved on the earth is a majO!: problem in the develop­ ment of the H-bomb. To find a practical way of initiating H-bombs will require much research and considerable time. HAT would be the effects of a hy­ bomb? Ridenour pOinted out that its power would be limited only by the amount of heavy hydrogen that could be carried in the bomb. A bomb carried by a submarine, for instance, could be much !llore powerful than one carried by a plane. Let us assume an H-bomb releasing 1,000 times as much energy as the Hiroshima bomb. The ra­ dius of destruction by blast from a bomb increases as the cube root of the increase in the bomb's power. At Hiroshima the radius of severe destruction was one mile. So an H-bomb would cause almost complete destruction of buildings up to a radius of 10 miles. By the blast effect alone a single bomb could obliterate al­ most all of Greater New York or Moscow or London or any of the largest cities of the world. But this is not all; we must also consider the heat effects. About 30 per cent of the casualties in Hiroshima were caused by Hash burns due to the intense burst of heat radiation from the bomb. Fatal burns were frequent up to distances of 4,000 to 5,000 feet. The radius of heat radiation increases with power at a higher rate than that of blast, namely by the square root of the power instead of the cube root. Thus the H­ Wdrogen bomb would widen the rilnge of fatal heat by a factor of 30; it would burn 20 © 1950 SCIENTIFIC AMERICAN, INC - people to death over a radius of up to 20 miles or more. It is too easy to put down or read numbers without under­ standing them; one must visualize what it would mean if, for instance, Chicago with all its suburbs and most of their in­ habitants were wiped out in a single flash. In addition to blast and heat radiation there are nuclear radiations. Some of these are instantaneous; they are emitted by the exploding bomb itself and may be absorbed by the bodies of persons in the bombed area. Others are delayed; these come from the radioactive nuclei formed as a consequence. of the nuclear explosion, and they may be confined to the explosion area or widely dispersed. The bombs, both A and H, emit gamma rays and neutrons while they explode. Either of these radiations can enter the body and cause death or radiation sick­ ness. It is likely, however, that most of the people who would get a lethal dose of radiation from the H-bomb would be killed in any case by flash burn or by collapsing or burning buildings. There would also be persistent radio­ activity. This is of two kinds: the fission products formed in the bomb itself, and the radioactive atoms formed in the en­ vironment by the neuh'ons emitted from the bomb. Since the H-bomb must be triggered by an A-bomb, it will produce at least as many fission products as an A-bomb alone. The neutrons produced by the fusion reactions may greatly in­ crease the radioactive effect. They would be absorbed by the bomb case, by rocks and other material· on the ground, and by the air. The bomb case could be so designed that it would become highly radioactive when diSintegrated by the explosion. These radioactive atoms would then be carried by the wind over a large area of the bombed counh'y, The radioactive nuclei formed on the ground would contaminate the center of the bombed area for some time, but prob­ ably not for very long because the con­ stituents of soil and buildings do not form many long-lived radioactive nuclei by neutron capture. Neuh'ons released in the air are finally captured by nitrogen nuclei, which are thereby transformed into radioactive car­ bon 14. This isotope, however, has a long half-life-5,000 years-and therefore its radioactivity is relatively weak. Conse­ quently even if many bombs were ex­ ploded, it is not likely that the carbon 14 would become dangerous. HE decision to proceed with the de­ T velopment of hydrogen bombs has been made. I believe that this decision settles only one question and raises a hundred in its place. What will the bomb do to our strategic position? Will it re­ store to us the superiority in armament that we possessed before the Russians obtained the A-bomb? Will it improve our chances of winning the next war if one should come? Will it diminish the likelihood that we should see our cities destroyed in that war? Will it serve to avert or postpone. war itself? How will the world look after a war fought with hydrogen bombs? I believe the most important question is the moral one: Can we who have al­ ways insisted on morality and human decency between nations as well as in­ side our own country, introduce this weapon of total annihilation into the world? The usual argument, heard in the frantic week before the President's deci­ sion and frequently since, is that we are fighting against a country whi�h denies all the human values we cherish, and that any weapon, however terrible, must be used to prevent that country and its creed from dominating the world. It is argued that it would be better for us to lose our lives than our liberty, and with this view I personally agree. But I be­ lieve this is not the choice facing us here; I believe that in a war fought with hydrogen bombs we would lose not only many lives but all our liberties and hu­ man values as well. vVhoever wishes to use the hydrogen bomb in our conflict with the U.S.S.R., either as a threat or in actual warfare, is adhering to the old fallacy that the ends justify the means. The fallacy is the more obvious because our conflict with the U.S.S.R. is mainly about means. It is the means that the U.S.S.R. is using, both in dealing with her own citizens and with other nations, that we abhor; we have little quarrel with the professed aim of providing a decent standard of living for all. We would invalidate our cause if we were to use in our fight means that can only be termed mass slaughter. We believe in personal liberty and human dignity, the value and impor­ tance of the individual, sincerity and openness in the dealings between men and between nations, prosperity for all and peace based on mutual trust. All this is in great contrast to the methods which the Soviet Government uses in pursuing its aims and which it believes necessary in the "beginning phase" of Communism -which by now has lasted 33 years. Regimentation of the private lives of all citizens, systematic education in spying upon one's friends, ruthless shifting of populations regardless of their personal ties and preferences, inhuman treatment of prisoners in labor camps, suppression of free speech, falsification of history in dealing both with their own citizens and witl1 other nations, violation of promises and treaties and the distorted interpreta­ tions offered in excuse of these viola­ tions-iliese are some of the methods of the U.S.S.R. which are hateful to the people of the Western World. But if we wish to fight against these methods, our methods must be clean. We believe in peace based on mutual trust. Shall we achieve it by using hy­ drogen bombs? Shall we convince the Russians of the value of the individual by killing millions of them? If we fight a war and win it with H-bombs, what history will remember is not the ideals we were fighting for but the methods we used to accomplish them. These meth­ ods will be compared to the warfare of Genghis Khan, who ruthlessly killed every last inhabitant of Persia. HAT would an all-out war fought hydrogen bombs mean? It would mean the obliteration of all large cities and probably of many smaller ones, and the killing of most of their inhabi­ tants. After such a war, nothing that re­ sembled present civilization would re­ main. The fight for mere survival would dominate everything. The destruction of the cities might set technology back a hundred years or more. In a generation even the knowledge of technology and science might disappear, because there would be no opportunity to practice them. Indeed it is likely that technology and science, having brought such utter misery upon man, would be suspected as works of the devil, and that a new Dark Age would begin on earth. We know what physical destruction does to the moral values of a people. We have seen how many Germans, ah'eady demoralized by the Nazis, lost all sense of morality when during and after the war the bare necessities of life, food, clothing and shelter were lacking. De­ mocracy and human decency were emp­ ty words; there was no restlrve strength left for such luxuries. If we have learned any lesson from the aftermath of World War II, it is that physical destruction brings moral destruction. We have also learned that prosperity is the best shield against communism and dictatorship, and in this knowledge we have poured billions into Western Eu­ rope to restore her economy. This gen­ erosity has won us more friends than anything else we have done. But after the next war, if it were fought with atomic and hydrogen bombs, our own country would be as grievously de­ stroyed as Europe and the U.S.S.R., and we could no longer afford such generosi­ ty. It would be everyone for himself, and everyone against the other. It is ironical that the U. S. of all countries should lead in developing such methods of warfare. The military meth­ ods adopted by this nation at the outset of the Second World War had the aim of conserving lives as much as possible. Determined not to repeat the slaughter of the First World War, during which hundreds of thousands of soldiers were sacrificed in fruitless frontal attacks, the U. S. high command substituted war by machines for war by unprotected men. But the hydrogen bomb carries mechani­ cal warfare to ultimate absurdity in Wwith 21 © 1950 SCIENTIFIC AMERICAN, INC defeating its own aim. Instead of sav­ ing lives, it takes many more lives; in place of one soldier who would die in battle, it kills a hundred noncombatant civilians. Surely it is time for us to re­ consider what our real intentions are. One may well ask: Why advance such arguments with reference to the H-bomb and not atomic bombs in general? Is an atomic bomb moral and a hydrogen bomb immoral, and if so, where is the dividing line? I believe there was a deep feeling in this country right after the war that the use of atomic bombs in Japan had been a mistake, and that these bombs should be eliminated from national arma­ ments. This feeling, indeed, was one of the prime reasons for President Truman's offer of international control in 1945. We know that the negotiations for con­ trol have not led to success as yet. But our inability to eliminate atomic bombs is no reason to introduce a bomb which is a thousand times worse. When atomic bombs were first intro­ duced, there was a general feeling that they represented something new, that the thousandfold increase of destructive power from blockbuster to atom bomb required and made possible a new ap­ proach. The step from atomic to hydro­ gen bombs is just as great again, so we have again an equally strong reason to seek a new approach. We have to think how we can save humanity from this ul­ timate disaster. And we must break the habit, which seems to have taken hold of this nation, of considering every weapon as just another piece of ma­ chinery and a fair means to win our struggle with the U.S.S.R. HAVE reviewed the moral issues that should deter us from using hy­ drogen bombs even if we were sure that we alone would have them, and that they would contribute to our victory. As Ridenour explained, the situation is rather the opposite. We can hardly ex­ pect to have a monopoly on hydrogen bombs. If we ever had any illusions about this, the events of the past few months should have destroyed them. The U.S.S.R. has the atomic bomb. She was undoubtedly helped in her efforts by the secret information she received from Klaus Fuchs, which presumably included many of the vital "secrets" of our project. But knowing how a group of scientists put the bomb to­ gether would not by itself enable a na­ tion to make orie. If Fuchs had given his information to Spain, for instance, it would hardly have been understood; it would presumably not have been used, and even if used it would almost cer­ tainly not have led to success. The prime requirements for the job still are a group of highly capable scientists, a country determined to make the weapon and a great industrial effort. We know now, if we ever doubted it, that the U.S.S.R. I has all of these. For the Soviet scientists the information must simply have re­ solved many doubts as to which steps to take next and saved a number of costly and futile parallel developments. Their obvious competence will pre­ sumably again bring success to the Rus­ sians when they try to develop the H­ bomb. Yet their decisions and their suc­ c�sses are not independent of our own. Our decision to make the H-bomb, which showed that we consideI:ed the project feasible, may well have prompted them to take the same decision. For this rea­ son I think that our decision, if taken at all, should have been taken in secret. This became impossible, however, when the advocates of the H-bomb used pub­ lic statements as a means of exerting pressure on the President. If the Russians were already working on the H-bomb before our decision, they will now have increased their effort. It is impossible to predict whether we or the Russians wiH have the hydrogen bomb first. We like to assume that we shall. If so, I refuse to believe that the U. S. would start a preventive war. That would violate all the fundamental be­ liefs of this nation, and that these beliefs are still strong is shown by the history of the past four years: although we had a monopoly of the atomic bomb we did not start a war. Clearly, then, the time will come when both the U.S.S.R. and this country will have H-bombs. Then this country will be much more vulner­ able than the U.S.S.R.: as Ridenour ex­ plained, we have many more large cities that would be inviting targets, and many of these lie near the coast so that they could be reached by submarine and per­ haps a relatively short-range rocket. I think it is therefore correct to say that the existence of the hydrogen bomb will give us military weakness rather than strength. UT, say the advocates of the bomb, what if the Russians obtain the H-bomb first? If the Russians have the bomb, Harold Urey argued in a speech just before the President's decision, they may confront us with an ultimatum to surrender. I do not believe we would accept such an ultimatum even if we did not have the H-bomb, or that we would need to. I doubt that the hydrogen bomb, dreadful as it would be, could win a war in one stroke. Though it might devastate our cities and cripple our ability to conduct a long war with all modern weapons, it would not seriously affect our power for immediate retalia­ tion. Our atomic bombs, whether "old style" or hydrogen, and our planes would presumably be so distributed that they could not all be wiped out at the same time; they would still be ready to take off and reduce the country of the ag­ gressor to at least the same state as our own. Thus the large bomb would bring B 22 © 1950 SCIENTIFIC AMERICAN, INC untold destruction but no decision. I believe that "old-fashioned" A-bombs would be sufficient to even the SCore in case of an initial Soviet attack with H-bombs on this country. In fact, be­ cause of the greater number available, A-bombs may well be more effective in destroying legitimate military targets, including production centers. H-bombs, after all, would be useful only against the largest targets, of which there are very few in the U.S.S.R. So we come finally to one reason, and only one, that can justify our building the H-bomb: namely, to deter the Rus­ sians from using it against us, if only for fear of our retaliation. Our possession of the bomb might pOSSibly put us in a better position if the U.S.S.R. should present us with an ultimatum based on their possession of it. In other words, the one purpose of our development of the bomb would be to prevent its use, not to use it. If this is our reason, we can contribute much to the peace of the world by stat­ ing this reason openly. This could be done in a declaration, either by Congress or by the President, that the U. S. will never be the first to use the hydrogen bomb, that we would employ the weap­ on only if it were used against us or one of our allies. A pledge of this kind was proposed in a press statement by 12 physicists, including myself, on Feb­ ruary 4. It still appears to me as a prac­ tical step toward relief of the interna­ tional tension, and toward freedom from fear for the world. The pledge would indicate our desire to avoid needless destruction; it would reduce the likeli­ hood of the use of the hydrogen bomb in the case of war, and it would largely eliminate the danger that fear of the H-bomb itself would precipitate a war. If we do not make this pledge, the hydrogen bomb would almost surely be used. Once war broke out, our military leaders would be blamed, iii. the absence of a pledge, if they did not immediately initiate a full-scale hydrogen-bomb at­ tack. But if such a pledge existed, they would be blamed if they did use the bomb first. To be sure, the pledge might not be relied on by our adversaries, but at least it would create a doubt in their minds and they might decide to wait and see. Perhaps they would not wish to provoke the certain use of the bomb by dropping the first one. Moreover, if they started a war, they would probably hope to capture our country and to exploit its wealth rather than to conquer a heap of rubble. ' We have proposed unilateral action rather than an international treaty on this pledge. We have done this because negotiations with the U.S.S.R. are known to be long and frustrating. A unilateral pledge involving only this country could be made quickly, and it could not again lead to the disappointment of a break- .-- :lown of negotiations. On the other hand, we certainly would not want to exclude on this subject. a pact with the U.S.S.R. This might be the first point on which the two countries could agree, and this In itself would be important. Obviously the pledge can only be a first step. What we really want is a workable agreement on atomic energy, as part of our efforts toward a lasting peace. Much has been said in the last few weeks about new negotiations on atomic contro!' Opinions vary from that of Senator Brien McMahon, who pro­ posed to spend $50 billion for rehab�li­ . tation of war-devastated countnes 111cluding the U.S.S.R. in exchange for an atomic settlement, to that of Senator Millard Tydings, who declared that an atomic settlement would not be accept­ able to this country unless it was coupled with general disarmament, which he has advocated for a long time. Both of these viewpoints, and those of many other Senators, show the desire of this coun­ try for some agreement. At the same' time there are persistent reports, clearly indicated in recent dispatches from the New York Times correspondent in Mos­ cow, that the Russians might like to negotiate. It seems to me that too much is at stake to miss any such opportunity. N the other hand, President Truman O voiced the fears of many of us when he stated recently that there is no se­ curity in agreements with the Russians because they break them at will. He re­ ferred to the agreements of Yalta and Potsdam in 1945. Since then we have learned much about Soviet methods, and the Russians have found that we do not retreat as easily as they apparently im­ agined in 1945. This more realistic mu­ tual appraisal makes it much more likely that we could now come to arrangements which neither side would regret after­ ward. Obviously in any negotiation each side must be willing to make con­ cessions and to consider primarily pro­ posals directed to mutual advantage rather than superiority over the other. The situation in atomic energy has changed, both because of the Soviet de­ velopment of the A-bomb and because of our decision on the H-bomb. To leave atomic weapons uncontrolled would be against the best interests of both coun­ tries. If we can negotiate seriously with the U.S.S.R., the scope of the negotia­ tions should probably be as broad as possible. But the situation would be greatly eased even if we could agree only to eliminate the greatest menace to civilization, the hydrogen bomb. • Hans A. Bethe, from 1943 to 1946 chief of the theoretical physics division at the Los Alamos Sci­ entific Laboratory, is professor of physics at Cornell University. .0000001 �-4-----+---4--�----4---� .000001 .00001 .0001 .001 .01 .1 1---+--1--- 10 100 1--' 1000 -_...I.--2.J.--3 .. 0 - ..1- -1- -----"--.1 - ---'-1 00 40 5 0 75 15 0 2 00 0 THE TIME REQUIRED for the nuclear reactions between deuterons (H2 nuclei) and each of the three hydrogen isotopes is plotted against tempera­ ture. The vertical coordinate is in seconds; the horizontal coordinate in millions of degrees Centigrade. Deuteron-triton reaction proceeds fastest. Sun's temperature is 6,000 degrees at surface, 20 million degrees at center. 23 © 1950 SCIENTIFIC AMERICAN, INC The Metamorphosis of Insects The phenomenon has long fascinated naturalists; now it sheds light on the forces that regulate growth and direct the specialization of cells by Carroll M. Williams HE human infant at birth contains ' about 10 trillion cells-the progeny of a single pair of cells derived from its parents. During the embryonic period of 10 lunar months, many of these cells possess the capacity for unlimited and disorderly growth. From experiments on animals we know that such cells, re­ moved from the early embryo and cul­ tured in a flask of nutrient solution, may grow aimlessly and without apparent restraint. Yet as long as they remain part of the embryo, their behavior is marvel­ ously coordinated. As if in conformity to some master blueprint, sooner or later each cell becomes committed to a precise and humble role in the final organism. During the embryonic period each cell also comes under influences that restrict its growth and multiplication; if it did not, the final result would be not an infant but a monster. The original ferti­ lized egg divides into two cells, the two into four, the four into eight, and so on through an average of ,43 divisions to produce the 10 trillion cells of the human infant. The process must stop right there. If the cells of the growing embryo un­ derwent 63 divisi9ns, say, instead of 43, the infant at birth would be larger than a sulfur-bottom whale. So the forces at work in the embryo must do two things: regulate the growth of the cells in the enlarging community and assign to each cell a specific role in the total organism. These forces obvious­ ly are not the exclusive property of the higher and more pretentious animals. Even in plants and animals too small to be seen with the naked eye, it is easy to show that the individual parts are held servant to a predictable and hereditary design of the organism as a whole. Evi­ dently the perfection of mechanisms for T controlling growth and differentiation was among the earliest accomplishments in the evolution of life. This being so, biologists have been able to study these mechanisms, so im­ pOltant to the human species, in a varied assortment of "beasts, fowl and creeping things." Indeed, it is fair to say that stud­ ies of the human species itself have made scant contribution to our present understanding of the matter; the bulk of our knowledge is based on studies of less intricate organisms ranging from oat seedlings to tadpoles. Particularly illu­ minating is the investigation of the metamorphosis of insects. Insects that metamorphose are especially interesting subjects for our study because in them the formative processes are prolonged throughout the life span, instead of be­ ing restricted to the period'of embryonic development, as in most other animals. Insect metamorphosis is an old story to biologists and students of natural his­ tory; it has recently been reopened with the fresh purpose of learning what it has to tell us about the basic problems of growth and differentiation. ONSIDER, for example, an extreme C type of metamorphosis" such as that of the fruit fly. The animal's life is par­ titioned into four distinct stages-egg, larva, pupa and adult. The pertinent events in its metamorphosis actually be­ gin within the unhatched egg. At this stage the eggshell encloses a yolk-filled space of no apparent structure. Under the microscope, however, the yolk par­ ticles are found enmeshed in a network of living protoplasm which surrounds a single centrally placed nucleus. It is this nucleus (more precisely, the genes on the chromosomes within the nucleus) 24 © 1950 SCIENTIFIC AMERICAN, INC that represents the hereditary blueprint of the future organism. In fact there is a double set. of blueprints, since the nucleus contains two complete sets of chromosomes and genes, one contrib­ uted by the paternal fly and the other by the maternal fly. What we shall wit­ ness is the orderly construction of an organism according to a detailed heredi­ tary formula. The first thing that happens after the egg has been fertilized is a subdivision of the single nucleus into two separate nuclei, followed by a further series of nuclear divisions. There is convincing evidence that each of these divisions is preceded by a duplication of each pair of genes. In consequence the multipli­ cation of nuclei does not dilute the genet­ ic material, although each nucleus is equipped with a full set of genes. The egg at this stage consists of a single yolk­ rich cell containing several hundred nuclei. As the latter continue to divide, they seem to be attracted towar.d the outermost region of the egg. Then for the first time cell boundaries are laid down around the nuclei and the single multinucleated egg is transformed into a hollow, yolk-filled ball of cells. Only those nuclei that are fortunate enough to land along the axis of the belly of the egg will contribute to the forma­ tion of the embryo itself. The vast ma­ jority come to rest elsewhere, and are destined to form embryonic membranes that are ultimately discarded. As the English biologist V. B. Wigglesworth has remarked, "the cells are but bricks; whether they play a noble or a humble part in the final building is decided by the chance of where they fall." Few phenomena in biology are as baf­ fling as the events that now take place: A B c D hegins with the fertilized egg (A), which grows into the larva (B). The organism then metamorphoses into the pnpa (C) and finally the adult fly CD). The single nucleus of the fertilized egg (inset) contains eight chromosomes, four from each LIFE OF THE FRUIT FLY parent. Indicated within the chromosomes are the genes, the· hereditary blueprints of the organism. Indicated in black within the larva are the imaginal disks, which develop into the pupa and the adult fly. The larval tissues indicated in red hreak down in metamorphosis. 25 © 1950 SCIENTIFIC AMERICAN, INC B c (i.e., the larva of the Cecropia moth) to the pupa is examined by experiment. Silkworm tissues require for metamor­ phosis a hormone secreted by the prothoracic gland (right inset). This gland must in turn be stimulated by a hormone secreted in the brain (left inset). Here three silkworms have been tied off into three compartments METAMORPHOSIS OF THE SILKWORM _ at three ages. Silkworm A is tied off before the brain hor­ mone (dots) is secreted; the silkworm fails to pupate. Silkworm B is tied off after the brain hormone has cir­ culated throughout its body, but before it has set off the prothoracic gland. The prothoracic hormone (circles) is restricted to the thorax, and only the thorax pupates. Silkworm C, tied off still later, pupates completely. 26 © 1950 SCIENTIFIC AMERICAN, INC From a region of the ovum that will form the future thorax, there arises an influ­ ence of unknown nature that spreads like a wave over the embryo. As it traverses the hollow ball of cells it casts the ma­ jority of the cells for the specific parts they will play in the future larval insect. A few hours later the same thoracic cen­ ter generates a second wave of deter­ mination that commits other cells to the formation of specific parts in the pupal and adult insect. Now, though the em­ bryo still consists only of a hollow, yolk­ filled ball of cells, the plans of two future organisms, the larval and pupal-adult insects, have already been roughed out. Two living systems exist side by side­ one destined to form the larva, the other the pupal and adult fly. p to this point any cell in the embryo U could have contributed to any part of the final insect, for each cell is equipped with a complete set of genes, and these are the blueprints of the total organism. With one swift stroke the in­ fluence of the thoracic center nas altered the cells' potentialities. Each cell con­ tinues to possess a full set of genes, but these genes now direct the cell toward a specific fate and function. Thus the cell accepts a specialized role in the organ­ ism by surrendering its other latent po­ tentialities. Now the cells committed to the forma­ tion of the larva rapidly execute their various developmental tasks. Within a few hours a tiny fly larva crawls from the egg. During the four days that fol­ low, the headless, footless, wingless larva grows rapidly, twice molting its skin. Curiously this growth of the fly larva occurs not by multiplication but solely by enlargement of the cells. When the larva matures it has no more larval cells than were present when it hatched from . the egg. Meanwhile the embryonic cells that were committed to the formation of the pupa and adult also are present, but take no part in the larva's domestic affairs. They are found scattered throughout the larva in the form of little nests of cells called "imaginal disks." These disks are held under biochemical restraint by a hormone circulating in the blood which prevents them from differentiating into the pupal and adult organs. Though the disks grow at approximately the same rate as the larva itself, their growth takes place by cellular division, not by enlarge­ ment. In other words, the growing fly larva is a kind of double individual, one within the other and each growing by a totally different method. When the larva is full-grown, its skin hardens and darkens, and the animal rounds into an oval mass. The larva is now motionless and seemingly dead, yet extraordinary events are occurring in­ side. The larval cells are indeed dying, but simultaneously the imaginal disks throughout the body spurt in growth and differentiate into the organs of the pupal insect. In this process the growing cells utilize the dead larval tissues as a kind of elegant culture medium. The net re­ sult is that the larval tissues are replaced by pupal tissues derived from the im­ aginal disks. Soon afterward the pupal organs are transformed into the compli­ cated structures of the adult fly. What can be learned from such a pe­ culiar sequence of events? For one thing we see that the fly larva is a rather dif­ ferent organism from the pupa and adult. The imaginal disks, the precursors of the mature animal, live a kind of paraSitic existence within the host larva and in the process of pupation appropriate the la�­ val corpse to nourish their growth. Thus the assets of the larva are finally liqui­ dated and reinvested in what may be re­ garded as a new organism. From such a life history a further im­ plication is self-evident. There must be some over-all mechanism of control whereby the death of one developmental system, the larva, is synchronized with the birth of a second developmental sys­ tem, the pupa and adult. This mecha­ nism fortunately has proved more ac­ cessible to experimental analysis than the earlier and more perplexing events oc­ curring in the egg. Indeed, some illumi­ nating experiments can be performed with no more equipment than a few doz­ en insects and a piece of string. B ECAUSE of their small size, fly lar­ vae are not as suitable for such experiments as certain larger larvae; for example, the Cecropia silkworm. The experiments consist in tying string around the insect's body in such a way as to divide the animal into two or more horizontal compartments. The most in­ teresting results are obtained when one ligature is placed transversely behind the head and another just behind the thorax, thereby dividing the larva into three compartments-head, thorax and abdomen. The isolated head promptly dies, but the behavior of the thorax and abdomen depends on the stage of maturity of the silkworm at the time of ligation. If a ma­ ture Cecropia silkworm is subdivided before the cocoon is spun, its metamor­ phosiS is completely arrested. Both the thoracic and abdominal compartments continue to live for several months, but neither can transform to the pupal state. This fact suggests that the pupation of the thorax and abdomen requires some factor derived from the head of the caterpillar. And this indeed is found to be the case, for if the same treatment is applied two days later, after the larva has finished spinning its cocoon, the thoracic compartment now undergoes pupation. Evidently during the period of the spinning of the cocoon the head releases the required factor. Further experiments show that the pertinent factor is a hormone which is secreted by about two dozen nerve cells within the brain. This brain hormone seems to have a limited function. Its principal role is to trigger the secretion of a second hormone by a pair of endocrine organs located in the thorax, the "prothoracic glands." The second hormone in turn acts on the im­ aginal disks to provoke the transforma­ tion of the larva into a pupa. The pro­ thoracic glands secrete this "growth and differentiation hormone" during a period of three days after being acted upon by the brain hormone. If ligatures are placed on the silkworm less than three days after the completion of the cocoon, the thoracic compartment undergoes pu­ pation, but the abdominal compartment does not. Only after the three-day period does the abdomen acquire the necessary concentration of growth and differentia­ tion hormone. These simple experiments demon­ strate that the insect brain is an unusual organ, serving as the highest center in both the nervous and the endocrine sys­ tems. A further strange finding is that the growth and differentiation hormone fr.om the prothoracic glands seems to act back on the braiIl to shut off the secretion of the brain hormone. Thus the endocri­ nological system of the insect is a kind of self-balancing mechanism, using a bio­ logical application of the "negative feed­ back" principle to regulate the flow of hormone. The brain and the prothoracic glands control not only the formation of the pupa but the development of the adult moth from the pupa. After the pupation of the Cecropia silkworm, the brain ceases to secrete its hormone for many months. This accounts for the state of dormancy in which the pupa spends the winter. The months of exposure to win­ ter's low temperatures serve to build up the brain's activity again. III the spring the brain releases its hormone and ter­ minates dormancy. Thus does the secre­ tory activity of the brain synchronize the life history of the animal with the seasons. ALTHOUGH our information is still incomplete, it seems probable that the growth and recurrent molting of in­ sects in the larval stage also require this very same growth and differentiation hormone. There is one important differ­ ence, however. During the period of larval life the tissues are exposed to a third hormone secreted by a tiny pair of glands located just behind the brain-the "corpora allata." If these glands are sur­ gically removed when the caterpillars are young and immature, the animals under­ go precocious pupation at the very next molt and ultimately develop into midget­ sized adult moths. It appears that this "juvenile hor- .tl. 27 © 1950 SCIENTIFIC AMERICAN, INC ANTERIOR HALF of a Cecropia pupa is cut off from the posterior half (below) and its brain removed. The fragment remains alive, but it cannot metamorphose. ANTERIOR HALF METAMORPHOSES of the pupa also remains alive after it is cut off from anterior. It lacks both brain and prothoracic gland, however, and cannot metamorphose. POSTERIOR HALF METAMORPHOSES POSTERIOR HALF mone" secreted by the corpora allata acts as a stabilizing factor during the larval life of the insect. It does not interfere with the growth of the imaginal disks or of the larva; it merely prevents them from proceeding further in their differ­ entiation. Late in larval life the corpora allata apparently are shut off by some unknown mechanism and discontinue the secretion of juvenile hormone. The imaginal disks, released from this bio­ chemical restraint, immediately respond to the growth and differentiation hor­ mone by differentiating into the pupal parts. And for the larval tissues the same transition signals biological death. In short, the stirring events that culminate in the fabrication of the pupa and the simultaneous death of the larval tissues are set in motion by the production of when a liv­ ing brain is implanted in it. The brain hormone causes prothoracic gland to liberate metamorphic hormone. when brain and prothoracic gland are implanted in it. The brain hormone again calls forth the prothoracic hormone. one hormone and the withdrawal of an­ other. Surveying our present knowledge of metamorphosis, it is difficult to avoid the conclusion that the post-embryonic development of an insect is the acting out of a sequence of roles which has been assigned the individual cells ac­ cording to a genetic formula during early embryonic development. Presumably as a result of the mysterious "waves of de­ termination" that sweep over the embryo at that time, each cell is endowed with a detailed program of differentiation, to the execution of which certain special­ ized tissues such as the brain, protho­ racic glands and corpora allata provide specific biochemical cues. Though much has been learned about the latter proc­ esses, we cannot yet pretend to under- 28 © 1950 SCIENTIFIC AMERICAN, INC stand the earlier mechanisms whereby the cells are made servant to the distant goals of the organism as a whole. For though each cell, as we have seen, is equipped with a blueprint of the total organism, its fate is decided by influ­ ences that are the common property of the entire growing system. Between the gene and the final or­ ganism as a unified going concern there is obviously room enough for the labors of a whole generation of biologists. Meanwhile we have cause to rejoice in the proof that the living organism knows what it is doing-and does it effectively. - Carroll M. Williams is as­ sociate professor of zool­ ogy at Harvard University. by radio­ 31) (11 acti ve iodine of rat thyroi d tissue on Kodak Autoradiographic Plate, Type No-Screen (X480) Autoradiograph New materials for IC AUTORADIOGRAPH RESEARCH tracer studies line of materials for Kodak announces a earch with topes, and for res with radioactive iso radioactive. substances naturally ak Auto­ kinds of plates: Kod There are twO new t speed; e No-Screen, for highes radiographic Plate, Typ a good for A, graphic Plate, Type and Kodak Autoradio both ... er pow ed and resolving combination of spe ons. with 25-micron emulsi histologi­ new advantages for g rin In addition, offe Stripping c phi gra dio Kodak Autora cal research, !there is on a ion uls em ron mic h its lOFilm, Type NTB, wit stripped off. film base that can be in autoce about problems Your corresponden . radiography is invited MPANY EASTMAN KODAK CO ROCHESTER 4, N. Y. © 1950 SCIENTIFIC AMERICAN, INC SCIENCE AND A Compact Analog Instrument that GROWS with Your Computing Needs Private laboratories. educational institutions. and public re­ search establishments call well afford the benefits of an ultra­ modern GAP/R Computor. This "building-block" computor. pronounced by authorities to be a superior tool of stud)' and development. operates automatically at electronic speeds, with no moving parts ... provides you with ncxiblc and Lasically useful equipment which may be expanded indefinitely merely by adding standard GAPIR Components. GAP/R BASIC COMPUTOR ASSEMBLY National Science Foundation HE bill to establish a National SciT ence Foundation, which had been SPECIFICATIONS Components: Regulated Power Supply, Ccntral Chassis, Plug: Panel, Rack and Accessories, 12 K3 Components (5 K3-C Coefficient Components, 3 K3·A Adding Components, 3 K3-J Integrating Components, 1 K3·L Unit-lag Com­ ponent). Excitation: Compound square· wave hasfXi 011 O. OOI�· seco·n d intervals. Connections provided for OtllCI forms vf cxcitation.: Presentation: Recurrcnt solutions for all variables, via one or mo�e oscilloscopes (not supplied), plottcd against time or agamst one another. Accuracy: Resolution for time and voltage Precision 170. nov, 60 · O.l'fo; Parametric 500 Power Supply: cycles, watts. Basic Computor Assembly, FOB Factory - 84200.00 Typical GAP/R Comput or Component Employed for the direct adjustment of local scnsitivit}' in analog assemblies. Outputs are plus and minus the input signal multiplied by the numcrieal dial sctting (0-100). Model K3·C Coefficient Component Limit indicat,)f Identifying lettcr Special scalc (ccntral \'aluc unity) Input signal jack T\cgati\'c output signal jack This componcnl is onc of a dozcn similar tYJlcs which are available from stock. Each perfonJls a specific dynamic or mathematical �perali?n, and is specially engincercd to play its parL most effiCiently III any computing assemblage. Convenient to usc, cconomicallO buy. and of wide applicability, our GAP/R Analog Computor Compollcnts arc now assisting study and de­ velopment programs in many different ficlds. Is it not probalJle thcy can help you too? Send your computing plans and problems to us lor recommendations. GEORGE A. PHILBRICK RESEARCHES,INC 230 Congress St., Boston, Mass. ANALOG COMPUTORS FOR RESEARCH & DESIGN held in the House of Representatives for nearly two years, began to show signs of emerging last month, but in a form that threatened to result in a stillbirth.The House passed and sent to the Senate a revised version of the bill to which many scientists objected. One of the major changes in the bill was an amendment, sponsored by Repre: sentative Howard A. Smith and unani­ mously accepted by the House on a voice vote, which would reqUire approval by the Federal Bureau of Investigation of everyone connected with the proposed Foundation. The amendment said: "No person shall be employed by the Foun­ dation and no scholarship shall be awarded to any person by the Founda­ tion unless and until the FBI shall have investigated such person and reported to the Foundation that such person is loyal to the U. S., believes in our system of government, and is not and has not been at any time a member of any organiza­ tion Cleclared subversive by the Attorney General or any organization that teaches or advocates the overthrow of the gov­ ernment of the U. S. by force .and vio­ lence." Another amendment, evidently prompted by the Fuchs case, would re­ quire FBI clearance of any foreign citi­ zen associated with the Foundation "in any way whatsoever." Another change in the bill that greatly disturbed its proponents was a sharp cut in the proposed funds for the Founda­ tion. The bill would limit the Foundation to $500,000 in its first year and to a maximum of $15 million asear there­ after, instead of the $20 million allowed in the bill previously passed by the Sen­ ate.Still other revisions forbid the Foun­ dation to support any research in the broad field of atomic energy without the 30 © 1950 SCIENTIFIC AMERICAN, INC _ consent of the Atomic Energy Commis­ sion, and direct the Foundation to con­ duct classified military research. The Federation of American Scientists asserted that Rep.Smith's FBI amend­ ment "strikes at the heart of scientific support of the legislation." It added: "There seems little doubt, conSidering that the amendment goes fai· beyond anything previously enacted for a Fed­ eral agency, that its intent is more to kill the bill than to protect security. H. R. 4846, as it emerged from the House, has been so altered that many scientists un­ doubtedly will want to reconsider the support they have long given to the legiS­ lation .... The Foundation is severely limited by budgei:ary and other restric­ tions-so severely as to raise serious doubts that it can make a Significant con­ tribution to the national science effort. In addition, the Foundation is open to distortion by military interest. Under H. R. 4846 as amended, we have not realized the hope of freeing basic re­ search from security limitations by segre­ gating such research in an exclusive agency. Finally, the bill contains provi­ sions profoundly repugnant to the tra­ ditions and aspirations of scientists." The Council of the National Academy of. Sciences also expressed to Congress its strong objection to the Smith amend­ ment. The Council said: "We are con­ vinced that this provision, if made into law, would so distort the purpose of the original bill as to work serious damage to the development of science in the U. S." Having passed the House, the bill went to a House-Senate conference com­ mittee for resolution of its differences with the Senate bill, which scientists favor. As this issue went to press, the Washington representatives of scientific organizations were seeking to persuade the conference committee to drop the objectionable amendments, particularly the one requiring FBI investigations. If they failed, it seemed likely that they would urge defeat of the bilL Atomic Spy HE celebrated case of Klaus Fuchs T atomic spy, came to a swift end las� month. Fuchs, a German Communist who went to England in 1933, became a wartime participant in the atomic bomb project and most recently was head of the theoretical physics division at the British atomic energy research center at Harwell, pleaded guilty to having trans­ mitted atomic secrets to agents of the U.S.s.R. He confessed to four specific contacts with these agents: in Birming­ ham, England, in 1943; in New York City in 1944; in Boston in February, THE CITIZEN 1945, and in Berkshire, England, in 1947. His trial in a British court did not disclose what information he had given, but it was stated to be considerable. Convicted of violation of the British Offi­ cial Secrets Act of 1911, Fuchs received the maximum sentence of 14 years in prison. A strange feature of the case was that the U.S.S.R. repudiated Fuchs' confes­ sion. Tass, the Soviet news agency, said that "Fuchs is unknown to the Soviet Government and no 'agents' of the Soviet Union had any connection with Fuchs." The case deeply disturbed atomic sci­ entists in Britain and the U, S., both be­ cause a scientist had betrayed his trust and because the affair promised to result in still further restrictions on scientific work in both countries. Yet they felt that if the Fuchs case had any lesson to offer, it was the essential futility of the great and growing structure of secrecy in the field of atomic energy. The fact that, in spite of the security precautions, atomic secrets had "leaked" was a proof of what many scientists had contended: that it is altogether impractical to expect to main­ tain the secrecy of a project that has em­ ployed hundreds of thousands of per­ sons. As a result of the Fuchs case, the negotiations among the U. S., Canada and Great Britain, looking toward an agreement for increased exchange of in­ formation and cooperation in atomic en­ ergy research among the three coun­ tries, were broken off. anl/tmeUttf a NEW SERIES of Offeril1gStlvil1gsUp To30% LARGE POLARIZING MICROSCOPE No. P39A RESEARCH POLARIZING MICROSCOPE No. P37A POLARIZING MICRO. SCOPE No. P40AC Increase 1900 the population of the S INCE U. S. has doubled; in a half-century it has grown as much as in the previous 300 years. This is the most striking fact in a mid-century review of vital statistics by the Metropolitan Life Insurance Company, which reports that the U. S. population is now well over 150 million. During the 50-year period the popula­ tion of California, the fastest-growing state, increased by 600 per cent, and that of the Far West as a whole by 400 per cent. Florida, Michigan, Oklahoma and Texas also had large gains. Among the cities Washington, D. C., had the most spectacular growth; its population tre­ bled. The lowest rates of increase, as is to be expected, were shown by northern New England and farm areas of the Mid­ west and South. In 1949 a new low in the U. S. death rate and a new high in life expectancy were recorded, according to statisticians of Metropolitan and the Federal Security Agency. Sharp decreases were reported in deaths from influenza, pneumonia, POLARIZING MICRO­ SCOPE No. P41 [l.C During the past five years two Spencer Polarizing Microscopes have been regularly equipped with Polaroid polarizers and analyzers. These have proven so successful that we are now offering Polaroid elements on every Spencer Polarizing Microscope. This means substantial savings to you, whether you buy the simplest or most elaborate. Experience has shown that performance is outstanding in every respec,t-durability, resistance to heat, American sensitivity of extinction point, image contrast, and freedom from residual color. Spencer Polarizing Micro­ scopes with Ahrens prisms are still available. These, together with the new series containing Polaroid rep­ resent the most extensive line of Polarizing Microscopes offered any­ where in the world today. Ask your AO Spencer Distributor to show. you the new Microscopes with Polaroid elements, or write Dept. D 178. � Optical co'" PAN V INSTRUMENT DIVISION . BUFFALO Il. NEW YORK 31 © 1950 SCIENTIFIC AMERICAN, INC ·!!T�FIR5"��� E (i{?1t#t6fieed ��a� COMPUTER • • • • tuberculosis, childhood diseases, child­ birth hazards, syphilis, appendicitis, rheumatic fever, typhoid fever, diarrhea and enteritis. "External hazards" have also been reduced: between 1911' and 1949 accidental deaths among Metro­ politan's policyholders fell 51 per cent, homicides 60 per cent and suicides 47 per cent. These successes make the dis­ eases of middle and old age, particularly chronic heart disease and cancer, the main causes of death now. The average life expectancy in the U. S. in 1949 was 67.8. Mortality in every age period has decreased, but most sharply in childhood and early adult­ hood. However, these cheerful statistics do not apply uniformly to all groups in the U. S. population. For example, the death rate among infants less than one year old in 1949 was only 32.2 per 1,000 for white babies, but almost twice that56.5 per 1,000-for "nonwhites." Oak Blight HERE seems to be some danger that T the lordly oak may go the way of the ... AN IDEAL all-purpose DIFFERENTIAL ANALYZER for Colleges, Universities and Industrial and Government Laboratories • In production manufacture for over three years, Reeves Electronic Analog Computers are now available for delivery as quickly as three months from initial order. Reeves' own well staffed Computing Center, meeting the challenge of varied techniques and requirements, keeps the design of REAC elements well in advance of latest develop­ ments in the field. Every new element is so designed that exist­ ing REAC instruments in the hands of users may be readily converted to peak efficiency. Latest instance of Reeves design--of special interest to the education field-are the new pre-patch type patch bays. These make possible the set up of complete problems without tie up of the REAC itself. REAC general purpose computers, put to use by outstanding organizations across the country, have demonstrated remark­ able practical values-by increasing the productive c.apacities of skilled personnel, by opening the economical approach to research and engineering problems through mathematics, by reducing computational costs as much as 95 %. As a result, REAC equipment pays for itself in a matter of months, often on a single project_ The REAC, constructed essentially of standard commercial electronic components, is easy to operate and maintain. Its accuracy, speed and versatility are more than adequate to handle great work-loads of mathematical computations. For complete description of REAC equipments and accessories write for Reeves booklet "RICO-2". 215 East 91 St., New York 28, N. Y. 32 © 1950 SCIENTIFIC AMERICAN, INC spreading chestnut tree. The oak trees of the U. S. face extinction by a microscopic fungus which is already well entrenched in the upper Mississippi Valley and is spreading east and south at the rate of about 50 miles a year. The organism, Chalara quercina, a relative of the fun­ gus that causes Dutch elm disease, was first observed and named in 1944. It was a fungus that virtually wiped out the American chestnut. Chalara quercina is known to attack at least 28 different species of oak. It kills the tree by clogging the channels through which water passes from the roots to the leaves. On red oaks its effects appear first in the upper crown. The leaves turn a dull light green, curl up­ ward, then turn yellow or brown. An infected tree may lose all its leaves with' in a month. Oak is one of the chief American woods, most commonly used for floors, railroad ties, mine props, barrel staves and furniture. In large areas of the east­ ern U. S. oaks make up 50 to 75 per cent of the forest cover. So far the fungus disease has spread to seven states, as far south as Paducah, Ky., and as far east as Gary, Ind. It has shown an ability to survive in a wide range of climates. In the hope of stop­ ping its spread, research workers of the U. S. Department of Agriculture are try­ ing to learn how it jumps from one local­ ity to another. An English Kinsey Report S EXUAL behavior is just as common in Britain as in the U. S., according to . a recent survey by Mass-Observation, a British opinion research organization. Britons refer to the study as "a sort of Gallup on a sort of Kinsey." Its results • were reported in the Public Opinion Quarte1'ly by L. R. England, director of Mass-Observation. The survey consisted of street inter­ views of 2,000 men and women, answers to a more intimate written questionnaire by 11 per cent of the interviewees and by 400 members of Mass-Observation's National Panel of Voluntary Observers, and answers to brief attitude question- . naires by a number of "opinion leaders" among doctors, clergymen and school teachers. In general the man (and woman) in the street differed rather widely from the opinion leaders in the attitude toward sexual behavior. Only 51 per cent of the street sample were unreservedly op­ posed to prostihltion, as against 93 per cent of the clergy. Only 58 per cent of the street interviewees- were unreserv­ edly in favor of marriage, whereaS' 75 per cent of the doctors, 80 per cent of the teachers and 90 per cent of the clergy favored it. "Most people feel that there is noth­ ing innately wrong or unpleasant in sex in itself," Dr. England reports. He found that attitudes were somewhat correlated with the sex, social class and religious belief of the respondent, but that reli­ gious belief had more effect on the in­ dividual's attitude than 011 his or her behavior. Premarital and extramarital sexual activity apparently are widely practiced among Britons as well as among Ameri­ cans. The main divergence from the Kinsey findings was that only 12 per cent said they had had physical homo­ sexual relationships. The traditional British reticence did not prevent most of the interviewees from answering Dr. England's questions. One exception was a clergyman, who wrote in response to his questionnaire: "I count it Infernal insolence on your part that you sent it to me." The survey was intended only as a preliminary outline for a more compre­ hensive study. Dr. England already has one conclusion to offer: "In the field of sex, as in many others, modern man is confused." Second Sound You can record torques instantaneously with the. BRUSH Strain Analyzer • Here's a strain measuring device that gives you accurate . . for your interpretation ... and for permanent proof of results. The Brush Strain Analyzer provides these advanta ges for a rapidly growing list of enthusiastic users, for a wide variety of applications. The picture shows Professor D. K. Wright, Jr. of the Mechanical Engineering Department of Case Institute of Technology, using this Brush Analyzer to record the torque of an engine equipped with fuel economizer. Professor Wright reports that the Brush Strain Analyzer is used at Case for research and tests involving torque, strain, vibration, pressure and other physical variables. you can benefit from the accurate measure­ proven results made possible by Brush Analyzers. Find out how ments and W ORKERS in the field of low-tem­ perature physics have been divided between two theories about the nature of helium II, the so-called "fourth state of matter." Helium II, a strange fluid produced when liquid helium is cooled below 2.19 degrees above absolute zero, possesses a number of unique properties, among them the ability to conduct heat at extraordinarily high speeds-a phe­ nomenon known as "second sound." To explain the peculiarities of helium II, Laszlo Tisza of the Massachusetts Institute of Technology and Fritz Lon­ don of Duke University postulated that helium II is a mixture of two fluids: 1) a immediate, records of static or dynamic phenomena . Write today for information. THE 'B'Z-� DEVELOPMENT COMPANY 3405 Perkins Avenue, Cleveland 14, Ohio, U. S. A. Canadian Represenlalives: A. C. Wickman (Canada) Ltd., it in � witIt P. O. Box 9. Station N, Toronto 14, Ontario a BRUSH RfCORDINC ANAlllfR STRAIN ANAlYZERS. SURfACE ANAlYZm • CONTOUR ANllIlUS • UMIiUSU ANAlIl£1! 33 © 1950 SCIENTIFIC AMERICAN, INC A new improved BETA GAMMA Scaler (Model K-281) Featuring Motor Driven Register Reset Built for Continuo'us Use SPECIFICATIONS SCALING STAGES-Scale of .64. 128. 256 by selector switch. Neon light for interpolation. Binary system. AUTOCOUNT-IO, 100, 1000 pre-set register counts. AUTOTIME-Outlet for pre-set timer (Model. K-214 Timer). HIGH VOLTAGE lized. Regulated. from 600-2500 V. POWER SUPPLY-Stabi­ Continuously variable Illuminated 4%" meter. RESOLVING TlME-5 microseconds. INPUT SENSITIVITy-Adjustable. Set at y. V. REGISTER-4 digit Veeder Root. Motor dri ven reset. TIMER. OSCILLOSCOPE. G. M. TUBE CONNECTORS. POWER REQUIREMENT-IOO to 125 V •• 60 cycle, 2 amp. WEIGHT: COLOR: 571bs. Grey Hammertone. DIMENSIONS: lOY, x 22 x 22 in. KELEKET PROSPECTOR Easy to Detect Uranium Government Offers: $10,000 Govern­ ment reward, guaranteed market, profitable prices for discovery of Uranium . . . easy to detect with Keleket "Prospector". Simple to op­ erate: Durable, 2 lb. prospecting in­ strument. Cost less, made by com­ pany famous for 50 years. Complete with headphones $48.50 F.O.B. Factory. DEALERS: Write for excellent proposition and open territories. ARE YOU ON THE MAILING LIST FOR KELEFAX? Kelefax is a new bi-monthly publication containing technical news for personnel engaged in nuclear radiation work and industrial instrumentation. No charge, just send us your name and address. INSTRUMENT DIVISION The Kelley-Koelt Manufacturing Company 24-4 E. 6th St. COVington, Ky. "normal" liquid, and 2) a "superRuid" consisting of atoms with the smallest pos­ sible heat energy. According to another theory, proposed by the Soviet physicist Lion Landau, the superRuid atoms pos­ sess no heat energy at all. Both theories accounted successfully for all observed properties of helium II at temperatures above 1.3 absolute, and both predicted the discovery of second sound. But be­ low one degree absolute they clashed. Here Landau predicted a sudden rise in the velocity of second sound, while the London-Tisza theory predicted a drop in velocity. The question has now been settled by two workers at the National Bureau of Standards, J. R. Pellam and R. B. Scott. U sing the adiabatic demagnetization technique to attain extremely low tem­ peratures and new methods of detecting and timing second sound, they measured the speed of second sound at tempera­ tures below one degree absolute for the first time. They found that, as Landau had predicted, the speed rose sharply. At 1.1 degrees absolute the speed of second sound was 60.4 feet per second; at a temperature between .5 and .7degree absolute it increased to III feet per second. The report concluded: "Low­ temperature scientists can now confi­ dently employ Landau's postulates in their research." This confirmation suggests the possi­ bility of producing extremely low tem­ peratures by new methods. When helium II is in contact with a surface with an opening less than .00001-inch in cliam­ eter, atoms of the superRuid pass through the opening and atoms of the normal Ruid are left behind. Because the superHuid atoms, according to Landau's theory, take no heat energy with them through the opening, it should be possi­ ble to go to lower and lower tempera­ tures by repeatedly passing helium II through small openings. romlcron C. G. Grand MICROPHOTOMETER Patent Pending' DETERMINING EXPOSURE TIME in PHOTOMICROGRAPHY Invaluable for _ _ M cRo­ DENSITOMETRY MICRO· COLORIMETRY RADIO· AUTOGRAPHS • removal from microscope un· necessary • adaptable to any standard microscope • readings are conveniently taken by mov­ ing a lever Write for Pamphlet SAl Also available 100 watt Zirconium arc lamp with highly corrected optics. PAUL ROSENTHAL 505 Fifth Ave. ANOTHER LANGUAGE Is © 1950 SCIENTIFIC AMERICAN, INC a MUST For Modern Scientists You Can Learn Easily. Quickly. Accurately With lllGUAPHOIE You learn through natural everyday conversa­ tion ...with effortless ease and real pleasure. First you LISTEN and in an amazingly short time you SPEAK, with correct accent and the right swing. In your own home you can study alone in privacy or �ave wife and children or friends join you in a delightful pastime and cultural necessity that is an essential asset whether science is your career or your hobby. It will take you only 20 minutes a day to master any of 29 important languages the . Linguaphone Way. HE problem of salvaging useful ma­ T terial from sewage, one of the most 34 New York 17, N. Y. Mic:roscopes & Sc:ientifie .Apparatus Phosphorus from Sewage conspicuous wastes of civilization, has long interested engineers, but it has been difficult to find economical ways of doing so. Now two engineers at the UniverSity of Wisconsin have developed a practical method of recovering phosphorus. Wil­ liam L. Lea and Gerard A. Rohlich have developed a process which uses alum as a coagulating agent. It produces a sludge from which phosphorus can be recov­ ered in the form of calcium phosphate, useful as fertilizer. Nearly all the alum can be separated and used again. Lea and Rohlich estimate that a ton of fer­ tilizer can be recovered daily from the 15 million gallons of sewage processed every day at the sewage plant in Madi­ son, Wis. At this rate the sewage of the cities of the U. S. would yield over 400,000 tons of fertilizer a year. • SPANISH PORTUGUESE ITALIAN FRENCH GERMAN RUSSIAN or any of 29 languages Linguaphone courses were made astonishingly sim.... ple, easy and practical by more than 150 expert linguists of international fame. Endorsed by educa­ tors, used by colleges, schools and the choice of more than one million home-study students. -----SEND FOR FREE BOOK----­ I I I I I I LINGUAPHONE INSTITUTE 20 Radio City. New York 20, N. Y. Send me Ihe FREE Linguaphone Book J wanl 10 learn.... Name...... ............. Language .. ....................................... ............................... l I I I I l ��;:=·=====i:�����:=:=:� J POWER TO BURN ... FRb� AIR! Chief among the startling new features of the radi­ cally designed Convair XP5Y-l, long range flying boat, is the first gas turbine pneumatic auxiliary power system ever built for aircraft_ It was designed by AiResearch Manufacturing Company in cooperation with the Navy Bureau of Aeronautics and Consolidated Vultee Aircraft Corporation. Vital to the system are the first air turbine-driven alternators for aircraft, which operate all major accessories. In the air they are operated by main engine bleed air from the new Allison T-40 turboprop engines. Each of the two alternator drives produces up t o 70 shaft horsepower and maintains constant rpm regard­ less of the varying accessory loads. When the airplane is afloat in some harbor or remote lagoon, power is supplied by t h e s y s t e m's s m a l l AiResearch gas turbines, making the XP5Y-l the first turbine-propelled airplane capable of maintammg heat, light, radio communication and all necessary accessory activity without operating the main engines. In addition, AiResearch pneumatic auxiliary power is utilized for starting the main engines. It is the first airborne starting system for turbine-propelled aircraft which makes possible an unlimited number of self starts without aid from any ground source of power. • Whatever your field -AiResearch engineers -designers and manufacturers of rotors oper­ ating in excess of 100,000 rpm-invite your toughest problems involving high speed wheels. Spec ial ized exper ience is also available in creat ing compact turbines and compressors; actuators with high speed rotors; air, gas and liquid heat exchangers; air pres­ sure, temperature, elec­ tro n ic and many other automatic controls. • An inquiry on your company letterhead will get prompt attention. AiResearch Manufacturing Co., Los Angeles 45, Calif. 35 © 1950 SCIENTIFIC AMERICAN, INC A COMPACT PHOTOMICROGRAPHIC DEPARTMENT • • ·911 01te 1Imt! This unit, properly supplemented, will handle all types of photomicrography. Every comp09'enr has been designed to give you new adaptability, speed, ease and efficiency WRITE in: for your copy of detailed, E·2IO, to 642-R St. Paul St., Rochester 2, N. Y. informative Catalog No. Bausch & Lomb Optical Co., Removal of phosphorus would not only produce fertilizer but would cut down one of the chief factors promoting nuisance growths of algae in lakes and rivers. The process could also be used to segregate dangerous radioactive phos­ phorus in the wastes of atomic research installations. Brain Waves of Murderers is a murderer responsible for WHEN his crime? According to the law, he is sane and subject to execution if he knows what he is doing and that it is "wrong." But psychiatrists would like to see a more scientific criterion for crimi­ nal insanity. An editorial in the British Medical Journal recently discussed some investigations of the brain waves of mur­ derers that may suggest such a criterion. D. Stafford-Clark and F. H. Taylor examined 64 prisoners, 58 men and six women, all charged with murder. They found that in 11 cases where the killing was in a sense unintentional, as in self­ defense, only one of the prisoners gave an abnormal electroencephalogram. Of 16 persons who had a clear criminal mo­ tivation, such as robbery, four showed abnormal recordings. Of 15 who killed with no apparent adequate motive, 11 showed abnormalities. Among 14 mur­ derers who were clinically insane 12, or 86 per cent, had abnormal brain waves. The Journal remarks: "The cases of inadequately motivated murder appear to present a new medical problem call­ ing for investigation, particularly since many of the prisoners in this group [ap­ peared] normal." Tuberculosis Test blood test to detect active A NEW tuberculosis was announced last Bausch &. Lomb �L Photomicrographic Equipment = SAVE95% ON PERIODICAL STORAGE SPACE "SCIENTIFIC AMERICAN and over 370 other leading periodicals are now avail­ able on microfilm-cost about equal to library 11M � binding_ Write for details." UNIVERSITY MICROFILMS ANN ARB 0 R, M I CHI G AN 36 © 1950 SCIENTIFIC AMERICAN, INC month by Sidney Rothbard of the Monte­ fiore Hospital in New York. The test is based on studies of virulent and avirulent tubercle. bacilli by Rene Dubos and G rdner Middlebrook of the Rockefeller Institute for Medical Research ( SCIEN­ TIFIC AMERICAN, October) . In Rothbard's test a -sample of the patient's blood is mixed with red blood cells taken from tuberculous sheep. The mixture is heated. If the patient has active pulmonary tuberculosis, the red cells clump together, and the degree of activity of the disease can be measured by the extent of clumping. The result is known within 24 hours. Rothbard re­ ported that the test had proved 92 per cent accurate in a sampling of 1,200 cases; in no case did it give-a false nega­ tive result. Since the standard tuberculin skin test does not show the state of activity of a tuberculous infection, and X-ray chest examinations often fail to distinguish lung lesions of tuberculosis from those of other diseases, the new test will aid greatly in diagnosis. PERFORMS A WIDE VARIETY OF TITRA­ liONS -Neutralization, Oxidation-Re­ duction, Precipitation, Complex-Forma­ tion and other types. N ow-Simpler, Faster, Automatic Titrations! NO SPECIAL TRAINING IS REQUIRED­ rapid and accurate titrations can read­ ily be performed without special skill or technique. QUICK, SIMPLE OPERATION-completes many routine cicracions in only 1-1 Y2 minutes-even titrations to 0.1% accu­ racy in.2 Y2 minutes or less. Change of sample is simple. rapid-a single motion raises. locates and secures new sample in operating posicion. Here's another new Beckman ad· vancement in instrumentation - an in· strument that runs your titrations for you. It's the Beckman Automatic Titra· CONVENIENT, VERSATILE, ADAPTABLE00 co 1000 C temperature compensa· cion .. . adjustable holder accommo· dates 10 ml to 400 ml beakers or simi· lar vessels ...instrument may be used with all standard burettes down to 5 tor-the instrument that makes accu· mi ...as many as four delivery units rate titrations more rapidly and con· trol unit .... uses standard Beckman veniently than by manual methods. accommodated by single amplifier conelectrodes ... electrode holders and delivery tip can be pivoted into any required position ... ample provision for mounting heating devices or other special equipment. such as preparing samples, or calculating series of titrations, simply fill the burette, place the sample in the beaker-a n d the Beckman Automatic Titrator takes over from there. Raising the beaker holder into posi­ tion automatically starts the stirrer motor and begins delivering titrating solution into the sample. A special circuit electrically anticipates results. � It eliminates the fatigue caused by close � It gives objective, reproducible rew/ts ... � It provides time-saving conveniences for observation required in manual procedures. ALSO A RELIABLE pH METER-the Beck­ man Automatic Titrator can also be used as an AC·powered pH meter co give accurate readings over che range o to 14 pH, as well as millivolt read­ ings from -600 to + 1400 mv. eliminates errors due to personal factors. sample handling. the approaching end point, scaling down delivery of the titrating solution in progres­ sively smaller increments to assure a highly accurate titration. When the end point is reached, delivery of the titrating solution" stops and a light shows com­ pletion 'of the titration-all automatically and without at­ tention from the operator. Whether your laboratory is large or small the Beckman Automatic Titrator provides important advantages in your titrating operations . . _ � It releases the technician dur­ ing titration, enabling him to perform other operations For full detail s on this new B e ck­ instrument see your au th o riz e d Beckman dealer-or write direct. man Beckmml Instruments, National Tech. nical Laboratories, South Pasadena 48, Califo rnia. Factory Service Branches: NEW YORK - CHICAGO - LOS ANGELES Beckman Instruments include: pH Meters and Electrodes - Spectrophotometers - RadioactiYity Meters - SpeCial Instruments 37 © 1950 SCIENTIFIC AMERICAN, INC THE S THETIC ELEMENTS There are nine of them, including the newly manufactured berkelium. Four have filled gaps in the periodic table of 92 elements and five have extended-it beyond uranLum T HE urge to take our material world al?art and identify its ultimate units of construction is at least as old as the early Greek philosophers. We have come a long way from their conclusion that all substances are variations of an Olympian brew composed of only four ingredients-fire, water, earth and air­ but the end of the quest is not yet in sight. At the moment the list of identified elements stands at 97. The physicists, of course, have broken these down into protons, neutrons and units which may be even more basic. In this article, how­ ever, we shall stop short of the subatomic world and confine ourselves to the ele­ ments, considering protons and neutrons only as they affect the elements' stability. From the strictly chemical point of view, the elements may be considered the blocks of which our universe is built. Our particular concern in this article will be the so-called synthetic elements, which for all practical purposes are not found in nature but are created only by the alchemy of the modern laboratory. Let us make clear at the beginning what we mean when we say that the synthetic elements are missing in nature. Actually tiny amounts of some of them, such as plutonium, have been detected in the earth, and all of them doubtless existed in considerable amounts at the primordial creation of the elements. But without exception they are so unstable that the original atoms must have disap­ peared long ago; any such atoms now found in nature are created only rarely by spontaneous nuclear reactions due to cosmic-ray bombardment or natural ra­ dioactivity. The idea that all matter could be re­ duced to a limited number of chemically indivisible elements began to take form in the 19th century. It developed prin­ cipally from the discovery of certain pe- by I. Perlman and G. T. Seaborg riodic similarities among the known ele­ ments. When the elements were ar­ ranged in the sequence of their atomic weights, it was found that elements oc­ curring at certain intervals on the list resembled one another in chemical properties. This resulted in the construc­ tion of a periodic table of the elements, which in turn disclosed some gaps. It was logical to assume that the missing chemical properties should be attributed to still undetected elements. With the discovery of X-rays and of the atomic nucleus at the turn of the century, a more meaningful picture of the differences among elements began to emerge. We now know that the dis­ tinguishing mark of each element-what determines its chemical properties-is the number of electrons it possesses, and that this in turn is uniquely determined by the number of positive charges or protons in the nucleus. The electrons are attached to the nucleus in successive shells, and as we go up the periodic table from the lower to the higher elements we find that the electrons closest to the nucleus are attached more and more firmly to the atom. The dislodging of one of these inner electrons is imme­ diately followed by an outer electron falling into the vacancy, and the energy released by this event appears as an X-ray. The wavelength of the X-ray is characteristic of the element. It was G. J. Moseley of England who dis­ covered this relationship and thereby was able to arrange the elements accord­ ing to atomic number and to tell precise­ ly which elements were missing. Gradu­ ally most of the gaps between hydrogen (atomic number 1) and uranium (atom­ ic number 92) were filled by the discov­ ery of new elements. By 1925 only four elements remained to be found: those of atomic numbers 43, 61, 85 and 87. H. 38 © 1950 SCIENTIFIC AMERICAN, INC As one might expect, a new element did not necessarily appear for the first time in pure form, nor did it assert its singularity. Some research workers may have handled substances in relatively pure form and failed to recognize them as new elements. More often new ele­ ments were reported which proved to be identical with previously known ele­ ments or mixtures. During the 1920s and 1930s a number of workers reported the discovery of elements 43, 61, 85 and 87. They gave these elements such names as masurium, illinium, florentium, alaba­ mine, virginium and moldavium, and to this day these names appear in some tables of elements. It is fairly certain, however, that none of these elements can exist in nature in quantities detecta­ ble by the methods of investigation then employed. Actually the unambiguous identification of three of the four ele­ ments (the exception: element 87) had to await their preparation by artificial means, and even element 87 can be pre­ pared more readily by transmutation than from natural sources. Stable and Unstable Isotopes To understand the transmutation of elements, we must turn to considerations of nuclear stability. An element, as we have hoted, is uniquely characterized by the number of protons in the nucleus. But the number of neutrons associated with a given number of protons may vary. This results in the existence of vari­ ous species of the same element, known as isotopes, which differ in weight and stability but not appreciably in chemical properties. Relatively few of the possible isotopes of any element are stable; in fact, of the 1,000 isotopes of the 97 ele­ ments known to date, only about 275 are stable. Several hundred unstable nuclei may yet be prepared, but probably few stable nuclei remain to be discovered. The paucity of stable nuclei is largely explained by the interconversion of pro­ tons and neutrons; a proton wjll change into a neutron or vice versa if there is a slight imbalance from a norm character­ istic of each region of the periodic table. The nucleus is much more stable if it has an even number of neutrons or protons. As a result each element with an odd number of protons has only one or two stable isotopes. The margin by which an isotope may be stable or unstable is indeed small when compared with the total amount of energy involved in binding together the components of a nucleus. In mod­ erately heavy nuclei the total binding energy is about 1,000 million electron volts, yet if one nucleus is bound more firmly by even .01 mev than another with one more proton and one less neu­ tron, the second nucleus will decay into the first. Such small irregularities in nu­ clear binding may deprive some odd­ numbered elements of the possibility of having even one stable isotope. Conse­ quently such an element, barring some freakish factor that prevented its most nearly stable isotope from decaying, would not be found in nature. It may be of interest to speculate how different our lives would be, if indeed we would be here at all, should certain elements be unstable. One element with only a single stable isotope, for example, is iodine. This element, as a constituent of thyroxine, the hormone of the thyroid gland, is vital as a regulator of growth and development and of the metabolic rate. It is difficult to visualize what form vertebrate animal life would have taken had this element been missing. Another element with but one stable isotope is gold. As well as we can measure it, this isotope, Au,07, is conSiderably less than one mev more stable than the artificial and highly unstable mercury isotope Hg1V7. If this situation were reversed, Fort Knox might still be used to store something, but it would not be gold. PLUTONIUM hydroxide is isolated in a few crystals at the bottom of a capillary tube. Sample was prepared at University of Chicago in 1942. CURIUM is so intensely radioactive that it glows by its own light in a water solution. Curium was discov­ ered at University of Chicago in 1944. PROMETHIUM nitrate is isolated as clustered crystals. The crystals in the original photomicrograph have been enlarged by about 30 diameters. TECHNETIUM is prepared in the compound ammonium pertechne­ tate. In original photomicrograph crystals were enlarged 16 diameters. The Missing Elements Below lead, element 82, only two ele­ ments are missing in nature. These are elements 43 (technetium) and 61 (pro­ methium) which, as we shall see, may be prepared artificially in radioactive form just as one may prepare radioactive isotopes of all of the elements. The form of instability responsible for the absence of elements 43 and 61 involves neutron­ proton interconversions. It is called beta­ instability, meaning that the nucleus emits beta particles, i.e., electrons, in attaining stability. Among the heavier elements another type of instability sets in. This type is a consequence of what may loosely be considered an overstuffing of positive 39 © 1950 SCIENTIFIC AMERICAN, INC HOT LABORATORY at the University of California provides facilities for working with highly radioactive elements, synthetic and otherwise. Elements are chemically manipulated behind a lead wall by remote control (below). BEHIND LEAD WALL is equipment for manipulating radioactive elements. At upper left is a mirror in which the manipulations may be observed. Some stages in the isolation of curium were carried out in this laboratory. 40 © 1950 SCIENTIFIC AMERICAN, INC charge in the nucleus. The nucleus has an urge to get rid of protons. The mecha­ nism for relieving its condition is the emission of alpha particles, or helium nuclei, composed of two protons and two neuh·ons. The reason this complex par­ ticle rather than a proton is emitted is simply that the helium nucleus is such a stable structure that it is more economi­ cal of energy to rid the nucleus of pro­ tons in this fashion than individually. By the time bismuth, element 83, is reached, alpha instability sets in as a general con­ dition. (Some nuclei do not exhibit their alpha instability, however; because their beta-decay rate is much faster than their alpha-decay rate.) These alpha-emitters have vastly varying lifetimes: some as short as a microsecond, others compara­ ble with the age of the earth. The point to be made here is that there are only three nuclei above bismuth sufficiently long-lived to have survived geological time-thorium, 232, uranium 235 and uranium 238. These isotopes are respon­ sible for the fact that the earth still has small amounts of the elements between 83 and 92, for the latter arise as products of the decay of uranium and thorium. Thus the existence of this small island of relative stability at thorium and uranium is the only factor preventing the termina­ tion of the periodic table at bismuth. As these three nuclei decay, they maintain their various products in equi­ librium with them, in amounts that de­ pend on their relative stability or half­ lives. For example, radium 226 is one of the decay products of U238. Since the re­ spective half-lives of these isotopes are 1,600 years and 4.5 billion years, the two are found together in the ratio of one part of radium to tlu'ee million parts of uranium, or a third of a gram of ra­ dium to a ton of uranium. Two of the elements with extremely short half-lives, elements 85 and 87, are almost missed completely in the radioactive-decay se­ ries; element 87 occurs in uranium only in the fantastically low concentration of a few parts per billion billion. In the case of element 85, the amount that has been detected in nature is much smaller. Such small quantities, of course, cannot be iso­ lated and are measurable only through their radioactivity. It is only by the grace of an odd com­ bination of unusual circumstances, by the way, that fissionable U235 still exists in the earth in sufficient quantity to pro­ vide us with nuclear chain reactors and atomic energy. U235 has a half-life of only .7 billion years, which means that more than 90 per cent has disappeared through radioactive decay during the three billion years of the earth's age. Thus only by the slenderest of margins does enough U235 remain in natural uranium to operate a nuclear reactor or to make its separation from U238 feasi­ ble. And this is only half the story. Re­ cent studies of alpha radioactivity have shown that U235 falls into a category of nuclei whose half-lives are longer than would be predicted from their decay energy-the principal factor influencing the half-life. Even among this group in which alpha decay is "forbidden," U235 is something of a freak. For its particular decay energy it might be expected to decay about 10 times more rapidly than it does; while even if its decay were only twice as raprd as it actually is, it would essentially have disappeared from the earth by this time. Above uranium, alpha-decay half­ lives again become quite short, so the transuranium elements of primordial origin are no longer present although there is every reason to believe that such elements were formed at the same time as the more stable ones. The longest­ lived transuranium isotope known to date, neptunium 239, has a half-life of only two million years, which is almost 100 times too short to have permitted the element to persist through geological time. is the hazard in handling these radio­ active substances when they are made in visible amounts. A good example is the curium isotope Cm242, the principal iso­ tope of curium that has been used for experimentation up to this time. This isotope has a half-life of only five months, and if it were possible to make one milli­ gram of it, its alpha radioactivity would' be 3.5 curies. This would be a consider­ able amount of radioactivity to work with. If it were spread uniformly over the entire state of New York (we de­ liberately refrain from spreading it here in California) , radioactivity could be de­ tected on every square foot of ground. Thus the experimenter has no alterna­ tive but to work with extremely small amounts of such isotopes. Ultramicro­ chemical methods have been creveloped, ONE ELEMENT, the synthetic rare however, which permit almost any type earth promethium, has a characterisof chemical and l)hysical measurement t'IC X-ray spectrum WI'tl1 two l'Ines. to be made on only a few micrograms to a milligram of an element. Element 43 Radiochemistry The first synthetic element to be created was technetium, element 43, What about the chemical behavior of which filled the gap in the periodic ta­ these unstable elements? Basically the ble between molybdenum and ruthe­ chemistry of a radioactive substance is nium. Technetium was definitely identi­ no different from that it would have if it fied for the first time by C. Perrier and were not radioactive. There is one prac­ E. Segre of Italy in 1937. A sample of tical difference in handling it, however, molybdenum that had been irradiated and this is that we can detect it even with deuterons in the University of Cal­ when it is present in vanishingly small ifornia cyclotron was sent to them. From concentrations. If it were not for this it they isolated a chemical fraction facility, most unstable nuclei would re­ which, on the basis of its radioactive main undiscovered, for they are found behavior, was distinct from all other or can be prepared only in unweighable known elements. Its chemistry con­ formed with what might have been ex­ amounts. Today the techniques of the new pected from element 43, an element in branch of study called radiochemistry the series known as Group VII. Such a make it possible to obtain a great deal group, as already indicated, is made up of information about chemical properties of elements in the periodic table that are and to carry through chemical separa­ chemically similar to one another betions with amounts of material far too cause they have the same number of small to handle by the usual methods of electrons in the outer shell. Further ex­ chemistry. By the mere analysis of a ploratory work showed that element 43 substance's radioactivity it is possible to was somewhat closer in properties to obtain semiquantitative information rhenium, the next heaviest element in about its solubility, its oxidation-reduc­ Group VII, than to manganese, the next tion potentials, its formation of complex lowest element in the group. Ten years ions and many other properties. later Segre suggested that element 43 Once the element has been identified be named technetium (Tc) , derived there is a great incentive for manufac­ from the Greek technikos, signifying the turing it in visible amounts so that one element's artificial or "technical" origin. can study its spectra, its crystal structure From the behavior of a certain isotope and many other properties that are in­ of technetium, Tc99, with a half-life of accessible to radiochemical method'S. six hours, it was deduced that this iso­ With the advent of the nuclear reactor tope must have another form, or nuclear the synthesis of these radioactive ele­ isomer, with a long half-life. Thus one of ments is no longer difficult, provided the the conditions for obtaining macroscopic transmutations can be effected with neu­ amounts of the element was fulfilled, trons. There are problems, however, in namely, that a long-lived isotope must connection with the elements' great r�­ exist. The other condition, a method of dioactivity. It is desirable to work with preparing the element in quantity, was an isotope with a relatively long half­ realized when it was shown that the six­ life, for if the half-life is short it may be hour Tc99 is a fission product and theredifficult to produce the element at a fore can be made in an atomic pile. The faster rate than it decays. Also important fission yield of technetium is high; Tc99 THREE ELEMENTS in succession, neodymium, promethium and samar· ium, have successive pairs of lines. TWO ELEMENTS, neodymium and samarium, have X-ray lines with a gap between them for promethium. 41 © 1950 SCIENTIFIC AMERICAN, INC PROMETHIUM ASTATINE 1 H I 3 4 5 6 7 9 10 8 n�,i III j p 12 N :. 11 12 13 14 15 16 17 18 fr� 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 -35 36 K C Sc Ti V Cr Mn Fe Co Ni Cu Zn.. Ga Ge As Se Br Kr .. 3d 4p 45 � 46 47 48 49 50 51 52 53 54 In Sn .Sb Te 1 Pd Ag C 37 38 39 40 :' Rb � 55 56 57 58 59 60 Cs B Ce Pr Nd - e:. La... 65 . I 5d I 1- __ .J .J 756d I "4�"5� 1 E':J 6p 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 . Sm Eu Gd Tb Dy Ho Er Tm Yb Ta W Re Os- lr Pt Au TI Pb Bi Po - __ __ _ 88 89 90 9T 92 Ac Th Pa U Ra X� 1 • 1 ______ ------ L:. Hf H:.. 4f 5d I _ ________ ___________ __ ____________ I 86 .: 5f ? . .: 6d ______________ __ _______ _ _ _ __ _____ 42 © 1950 SCIENTIFIC AMERICAN, INC : .. 7p constitutes 6.2 per cent of the eventual fission products in a pile, and it can be calculated that the fission of one gram of U235 produces 26 milligrams of Tco9• The element can also be made by irra­ diating molybdenum with neutrons to form Moo9, which decays to Tc90; so two methods for production in quantity are available. When it became possible to produce suitable amounts of long-lived Tco9, it turned out to have a half-life of close to one million years. With this half-life the element becomes relatively easy to han­ dle. A number of milligrams have now been isolated and many of its chemical properties have been investigated. Like the brilliant violet permanganates fa­ miliar to chemists, the corresponding pertechnetates are also brightly colored. Technetium has been prepared in the metallic state and combined in a number of compounds; its optical emission spec­ trum and X-ray spectrum have been recorded; its mass number has been proved to be 99 by means of the mass spectrograph. It is almost certain that there can be no primordial technetium in nature, since all possible isotopes of the element seem to have half-lives which are far too short. The only processes that come to mind as possible sources for the con­ tinuing formation of technetium in na­ ture are (I) the spontaneous fission of U238, a very rare event, and (2) the ac­ tion of stray neutrons on molybdenum and U235. If we assume that the yield of Tc99 from the spontaneous fission of U238 is the same as that from the neu­ tron-induced fission of U2:l5, and that the half-life of spontaneous fission is 1016 years, then each kilogram of uranium when dug from the ground would con­ tain only a few millionths of one micro­ gram of Tc99• The other mechanisms for producing Tc99 would not yield much more. Element 61 The next synthetic element we shall consider is the rare earth promethium. The rare-earth elements are a group from cerium to lutetium (atomic num- bers 58-71 inclusive). They are closely allied in chemical properties to one an­ other and to their prototype, lanthanum (element 57). The rare earths always occur together and have a marked pre­ dilection for remaining together under most chemical treatments. The classical method for separating them is repeated recrystallizations, a most laborious and material-consuming process. When the rare earths were finally lined up according to atomic number, the space for element 61 remained un­ filled. Obviously the place to look for element 61 was in rare-earth ores, but the difficulty of separating rare earths from one another was an obstacle. Al­ though a number of claims to its dis­ covery were made, the question of the existence or nonexistence of element 61 in nature was still unsettled when the possibility of preparing il* artificially presented itself. Several groups of in­ vestigators irradiated neighboring rare earths and produced some new sources of radioactivity, some of which undoubt­ edly were isotopes of element 6l. But which radioactivities belonged to ele­ ment 61 and which to new isotopes of known rare earths? T�is question re­ mained unanswered because the meth­ ods of fractionating rare earths were of insuperable difficulty and .the radioac­ tivities observed had short half-lives. Two developments in the Manhattan Project during the war conspired to al­ low the unambiguous discovery of ele­ ment 6l. Foremost was the development of methods for.separating the rare earths by means of synthetic ion-exchange resins. It was found that neighboring rare earths could be largely separated in one pass through a glass column filled with resin. Furthermore, the rare earths came off the column in a definite order, inversely as the atomic numbei', so that it was fairly safe to assume that element 61 would follow samarium, element 62. The second important discovery was that a relatively long-lived isotope of element 61 occurs as a result of uranium fission. The first positive identification of element 61- came in 1945 from the ex­ periments of J. A. Marinsky and L. E. Clendenin at the Clinton (now Oak THE PERIODIC TABLE at the bottom of the opposite page presents the 97 natural and synthetic elements in horizontal rows to show similarities in their chemical properties. Elements of similar chemical properties are connected by the lines running from top to bottom. Above the symbol of each element is its atomic number, i.e., the number of positive charges in the nucleus or the number of electrons bound by them. The nine syn­ thetic elements are indicated in red. In each horizontal row is one or more half-brackets designated Is, 2s, 2p and so on. Each of these brackets denotes the filling of a shell of electrons-more properly a subshell-in the succession of the elements. The electron shell structures of two synthetic elements are given in the schematic drawings at the top of the page. In X-ray terminology the shells are designated K, L, M, N, 0 and P. In spectro- Ridge National) Laboratory. They sug­ gested that the element be named pro­ methium (Pm) to draw a parallel be­ tween mankind's newly acquired nuclear power and the acquisition of fire, which according to Creek mythology was stolen from the gods and given to man by Prometheus. The longest-lived known isotope of promethium, Pm147, has a half-life of 3.7 years; nevertheless it has been iso­ lated in the pure state. At the Oak Ridge National Laboratory C. W. Parker and P. W. Lantz obtained promethium from a fission-product mixture, and B. H. Ketelle and C. E. Boyd isolated some from neutron-irradiated neodymium. Element 85 ' Let us now consider the third of the four gaps in the periodic table, element 85. The synthesis of this element actually came second chronologically, before promethium. Its manufacture presented a somewhat different problem from that of technetium and promethium. Tech­ netium can be made by irradiating molybdenum, the next lowest element, with neutrons or deuterons; promethium similarly can be made from neodymium, the next element below it. But in the case of element 85 the next lowest ele­ ment, polonium, itself exists only in trace amounts in nature. Hence polonium can­ not serve as the starting material. To make element 85 one must start with the element two numbers below it: bismuth. Consequently it is necessary to add not one but two charges, transmuting ele­ ment 83 to 85. This can be done by irra­ diating bismuth with accelerated ions of helium, which has two protons. The syn­ thesis was first accomplished by D. R. Corson, K. R. MacKenzie and Segre at the University of California (to which Segre had come from Italy). They named element 85 astatine, from the Creek word meaning "unstable." The -ine ending means that the element is a halogen, i.e., a member of the chlorine family. The particular isotope of astatine first made was At211, an alpha-particle emit­ ter. As a matter of fact, it exhibits a phe- graphic terminology they are designated 1, 2, 3, 4, 5 and 6. The spectrographic suhshells are designated s, p, d and f. The maximum numher of electrons in any s suh­ shell is two, in any p suhshell six, in any d suhshell 10 and in any / subshell 14. The numher of electrons in each suhshell is indicated hy a superscript; for example 6p5 in the outermost suhshell of astatine (At) indicates that there are five electrons in the p suhshell of shell 6. In the case of astatine all the suhshells are filled except the last. The case of promethium (Pm) and the other rare earths, however, is more complex .. In the rare-earth series from cerium (Ce) to lutetium (Lu) the numher of 5d and 6s electrons remains the same; in successive elements electrons are added in the 4/ suhshell. Prome­ thium thus has four 4/ electrons. The transuranium elements appear to helOllg to a second rare-earth series. 43 © 1950 SCIENTIFIC AMERICAN, INC nomenon known as "branched decay," which means that some atoms break down in one way and some in another, both sequences yielding alpha particles. One part of a sample of astatine emits alpha particles directly� thereby decay­ ing to bismuth 207; the other part first captures an electron and becomes polo­ nium 211, but the latter is extremely short-lived and promptly gives off a very energetic alpha particle. As a result, At211 is observed to decay with two alpha particles of widely differing ener­ gies. When observed with proper radia­ tion-measuring equipment, this isotope is as distinctive as a cat with two heads. The nuclear properties of astatine iso­ topes have been well charted and they lead to the conclusion that probably )'10 species of this element will have a half­ life greater than several hours. The chemistry of astatine has been investi­ gated on the tracer scale by the methbds of radiochemistry. Its behavior is that of a halogen conSiderably more electro­ positive than iodine, just as iodine is more electropositive than the next light­ est halogen, bromine. One means of separating astatine from solutions is by electroplating or chemical plating. There is no easy way to prepare astatine in visi­ ble amounts, for its longer-lived isotopes can only be made by the use of a parti­ cle accelerator such as a cyclotron. Even these have half-lives of only a few hours, so that work with macroscopic quanti­ ties will be exceedingly difficult because of the intense radioactivity. Element 87 The fourth and final gap in the peri­ odic table was element 87. According to its place in the table, this element should be a member of the alkali family, which includes sodium, potassium and cesium. As in the case of the other miss­ ing elements, there had been a number of claims to the discovery of element 87 by conventional chemical methods; the substance so identified had been variously called virginium and molda­ vium. But we now are virtually certain that there can be no stable isotope of element 87, and furthermore the longest­ lived known radioactive isotope of the element has a half-life of only about 20 minutes, so it could not have been de­ tected by conventional chemical meth­ ods. Actually element 87 was first discov­ ered unmistakably through its radio­ activity, and it was found as a product of the decay of a heavy element. To understand how it was identified, we must examine briefly the various proc­ esses by which the elements at the heavy end of the periodic table decay. There are three separate decay series among the natural heavy elements, known re­ spectively as the thorium, uranium and actinium series. The first series starts with thorium, which breaks down by a number of steps through various isotopes of radium, actinium, polonium and other heavy elements until it finally becomes stable lead. The second series starts with uranium and goes through a number of transformations into other isotopes of these elements until it, too, degenerates to stable lead. The third series, starting with actino-uranium, or U235, proceeds through actinium, from which the series derives its name, and finally ends as still another stable isotope of lead. Soon after the significance of these decay processes became understood, and it was realized that a number of isotopes of elements between uranium and lead should be found as decay products, at­ tempts were made to locate some isotope of element 87 in a decay sequence. Ele­ ment 87 of course stands above lead, element 82, ;0 it should be found some­ where in one of these series. It soon be­ came obvious, however, that no isotope of element 87 would result from the known breakdowns in the main pathway of any of the three decay series. But in 1914 Stefan Meyer, V. F. Hess and F. A. Paneth of Austria noted that actinium, Ac227, which was known as a beta­ emitter, also decayed occasionally by alpha emission. Since. actinium is ele­ ment 89, its alpha-decay product must be an isotope of element 87, in this case 8722:l. It was not until 1939, however, that Mlle. M. Perey of France suc­ ceeded, by very meticulous radiochemi­ cal separations, in obtaining a 21-min­ ute beta-particle emitter which she proved to be the alpha-decay product of Ac227. She later named this new element francium in honor of her native land. The three natural radioactive series, as we have observed, almost miss ele­ ment 87 completely. But when the arti­ ficial transuranium element neptunium was synthesized, a fourth series, starting with that element, was discovered. And this series yields an isotope of francium, Fr22\ in its main decay sequence. This isotope arises from the alpha decay of Ac225. It has a half-life of only five min­ utes, decaying by alpha emission to an astatine isotope of .02-second half-life. Subsequently it was found that Fr221 is also obtained as a decay product in a sequence starting from the artificial iso­ tope thorium 233 (see page 45) .. The short half-lives and inaccessibility of the francium isotopes have discour­ aged chemical investigation of the ele­ ment. It appears to behave like an al­ kali element in solution; one item of note is that francium has great volatility when the solution is evaporated to dry­ ness and brought to a temperature of several hundred degrees. This is a prop­ erty of alkali elements that begins to be prominent with cesium and is accen­ tuated with francium. Thus the gaps in the classical periodic system, covering the elements from hy- 44 © 1950 SCIENTIFIC AMERICAN, INC drogen to uranium, are now completely filled. We turn next to the transuranium elements. Beyond Uranium The search for transuranium elements, a quest born of scientific curiosity, was destined to be the trigger for a series of events which within a decade were to rock the world and burst upon the consciousness of every literate human being. These events, of course, were the discoveries that led to the exploitation of nuclear energy, in particular as a weapon of mass destruction. Other fun­ damental scientific discoveries undoubt­ edly have had equal or greater effect on mankind's mode of existence in the past, but none literally exploded in his face as has this one. In 1934 Frederic and Irene Joliot­ Curie of France made the exciting ob­ servation that an ordinary stable ele­ ment could be made radioactive by ir­ radiating it with alpha particles of natural origin. This discovery of artificial radioactivity immediately stimulated research toward preparing radioactive forms of many elements. Two other ex­ tl'Eimely important developments were taking place at about the same time. One was the development by E. O. Lawrence at the University of California of the cyclotron, which was soon able to accelerate charged particles to energies far beyond those of naturally occurring alpha particles. This discovery made it possible to bombard and transmute the heavier elements for the first time, for alpha particles from natural sources can penetrate the nuclei of only the lightest elements. The second development wu, the discovery by James Chadwick of England of the neutron, an uncharged particle capable of entering any nucleus easily. Neutrons will literally fall into any nuclei at which they are directed. Since neutrons could be prepared by directing radium alpha-particles at a light element such as beryllium, it be­ came possible for anyone who could ac­ quire 100 milligrams or so of radium to produce and study the transmutation of elements. Most prominent in such stu­ dies was a group working with Enrico Fermi of Italy. They soon found a meam of preparing transuranium elements by· making use of the great avidity of nuclei for neutrons. It was already known that if the heavi­ est stable isotope of an element captured a neutron, the nucleus became unstable and decayed to the next higher element by beta emission; this method, as we have seen, can be used to produce tech­ netium from molybdenum and pro­ methium from neodymium. Suppose this process were applied to uranium, the heaviest element. U238 should capture a neutron and become a heavier isotope, Uno, which would be beta-unstable and decay to element 93-a brand-new ele­ ment outside the periodic table! When this experiment was tried, the experi­ menters experienceq a shock: instead of observing just one or two radioactivities from the product, they found a be­ wildering array of radioactivities. For some time it was thought that these ac­ tivities must represent a number of new transuranium elements. Not until several years later was it recognized that the activities came from fission products. Thus the discovery of fission was a by­ product of the search for transuranium elements. With poetic justice the actual dis­ covery of the first transuranium ele­ ment in turn resulted from experiments aimed at understanding the fission proc­ ess. Several experimenters, including E. M. McMillan of the University of California, measured the energies of the two main fission fragments by ob­ serving the distances they h'aveled from each other as � result of their mutual recoil when the nucleus exploded. Mc­ Millan noted that there was another radioactive product of the reaction, with a half-life of 2.3 days, which did not re­ coil, at least not sufficiently to escape from the thin layer of fissioning uranium. He suspected that this was a product formed by neutron capture, which does not release much energy, rather than by fission. McMillan and P. H. Abelson early in 1940 deduced by chemical means that this product was surely an Isotope of element 93, arising by beta decay from U239. The latter had a half­ life of 23 minutes'. Element 93 was given the name neptunium (Np) because it was beyond uranium, just as the planet Neptune is beyond Uranus. About this time the possibility of a nuclear chain reaction and the produc­ tion of transuranium elements for mili­ tary use began to take shape. With the war already in progress, further work on the transuranium elements and re­ lated subjects was conducted by physi­ Cists and chemists under self-imposed secrecy, at first informally and finally as an organized program. A neptunium isotope of great practical interest is Np237, discovered in 1942 by A. C. Wahl and Seaborg at the Univer­ sity of Galifornia. It is very long-lived (half-life: two million years) and can be made in appreciable amounts as a by­ product in the uranium pile. Because it is relatively innocuous, it can be handled experimentally in principle like any nor­ mal element. It was not obvious a priori what the electronic configuration and chemical properties of neptunium might be. Uranium was known to have some simi­ larity to tungsten and it was thought that element 93 might be a homologue of the next element above tungsten, rhenium. Yet there was also a possibility that ele­ ment 93 might be a member of a new URANIUM PROTACTINIUM THORIUM ACTINIUM RADIUM FRANCIUM NATURAL FRANCIUM is the result of rare branched decay of actinium 227. Ninety-nine per cent of Ac227 decays by beta emission to thorium 227. An almost negligible amount decays by alpha emission to francium 223. I uml ; URANIUM , tJj I ; PROTACTINIUM I I THORIUM ACTINIUM RADIUM FRANCIUM I 'I f l Fr221 SYNTHETIC FRANCIUM is made in appreciable quantity by irradiating thorium 232 with neutrons. The irradiation forms Th233, the starting point of this table. The decay proceeds through five other isotopes to francium 221. 45 © 1950 SCIENTIFIC AMERICAN, INC transition series among the heavy ele­ element's electrons, whether this is ac­ ments, similar to the rare-earth group. complished by the specific method of It turned out that neptunium bears no , adding oxygen or by any other means. resemblance to rhenium. It is much more "Oxidation state" is a somewhat more closely allied to its neighboring element rigorous term for what we used to call uranium. The evidence is mounting that the "valence" of an element.) Only a all of the transuranium elements belong few rare earths can be induced to as­ to a new transition series analogous to sume oxidation states other than the the rare-earth group. The transuranium trivalent, and these with difficulty. The elements parallel the rare earths in elec­ heavier elements, notably uranium, nep­ tronic configuration and have some tunium, plutonium and americium, are strong resemblances to them in chemical distinctly multivalent, with the trivalent properties. Just as lanthanum is the pro­ state becoming progressively more stable totype element for the rare-earth series, along the series. Thus trivalent thorium so actinium is the prototype for the cannot be obtained in aqueous solution; heavy-element series. Hence the new uranium can be reduced to this state group may be called the actinide series. only with difficulty; plutonium can be The members of this series known in na­ reduced to it fairly readily; for americi­ ture-thorium, protactinium and urani­ um it is the principal state, and for curi­ um-had not appeared to be related um it is the only one known. 'chemically, but when the transuranium The effort brought to bear on under­ elements were studied latent similarities standing plutonium chemistry has ele­ in the whole group began to appear. Be­ vated it to the status of one of the com­ cause of certain differences in chemical mon elements, insofar as knowledge of properties the theory that these ele­ its chemical properties is concerned. ments belong in one series is not ac­ The pronounced multivalent nature of cepted by all chemists. It is possible to an element such as plutonium makes it answer the objections on the basis of a of great interest in chemical studies, for detailed analysis of the evidence, but this single element affords means of ob­ this is not the place for such a discus­ serving most of the phenomena of inor­ sion. ganic chemistry. Plutonium is perhaps Let us note a few points here, how­ unique in having four different oxidation ever, on the chemical properties of states, which coexist in easily measurable these heavy elements as a group and concentrations in aqueous solutions. The their comparison with the rare earths. color changes from one oxidation state The rare-earth elements are predomi­ to another afford a fitting visual accom­ nantly trivalent, or in what the chemist paniment to the curious existence of the now calls the "plus three oxidation state." many states. Plutonium in its trivalent (Most chemists now use the term "oxi­ state in solution is a beautiful pure blue; dation" to signify the removal or neutral­ it changes to green or amber (depending ization through bond formation of an upon solution conditions) when oxidized '�__-7_2_1 CURIUM" to the quadrivalent state. The next state, pentavalent plutonium, is colorless; the highest oxidation state, six, is bright yel­ low. It is unfortunate that plutonium, because of its radioactivity, may never be suitable material for classroom use, for it has superb attributes as a teaching material. Element 94 After neptunium plutonium was of course the next element discovered; its name derives from the fact that Pluto is the next planet beyond Neptune. The work of McMillan and Abelson had shown that Np239 decayed by emission of beta particles; therefore the product should be the next higher element, num­ ber 94. However, the new element de­ cayed so slowly that it could not be definitely detected through its radioac­ tivity. By the end of 1940 Seaborg, Mc­ Millan, J. W. Kennedy and A. C. Wahl did discover element 940y a somewhat different approach. By irradiating urani­ um with deuterons they made a new isotope of neptunium which also de­ cayed to plutonium, but in this case the plutonium was sufficiently short-lived to allow its detection. This isotope of plu­ tonium has proved to be PU238, with an alpha-decay half-life of 90 years, while that for PU239, the first isotope made, is 24,000 years. Armed with the information on the chemistry of the new transuranium ele­ ments, Kennedy, Seaborg, Segre, and Wahl in 1941 were able to identify PU239 from strongly irradiated uranium and were able to prove that PU239 would � t: 21 6 2 0�_ 2_2_1_t" 9-r_2_ 1' 7-4__ 21�8-+ 2�1� A MERICIUM PLUTONIUM -t-----t-t-----+-�_ ----t---r--i ____t__t_- ,NEPTUNIUM __ -+ ____ t---____:___;____+-�-� URANIUM PROTACTINIUM THORIUM ACTINIUM RADIUM I ! Ac'" --�----+---� - ---+--�--+­ Ra'" FRANCIUM EMA NATION A STATlNE_ POLONIUM BISMUTH LEAD THE URANIUM SERIES of radioactive elements is mapped on the basis of atomic number or number of protons in the nucleus (column of elements at left) and atomic weight or number of protons and neutrons in the nucleus (numbers at the top) . In nature (red sym­ bols and arrows) the series begins with uranium 238, which decays through 13 other isotopes to stable lead 206. The series has now been enlarged (black symbols 46 © 1950 SCIENTIFIC AMERICAN, INC i � undergo fission with slow neutrons. The Element 96, found by Seaborg, R. A. most intensive cyclotron irradiations James and L. O. Morgan, was actually ever made were then carried out, with discovered before element 95. It was the objective of synthesizing sufficient made by the bombardment of plutonium plutonium to determine certain prop­ with alpha particles in a cyclotron. This erties that could best be obtained with produced an isotope of mass number visible amounts. In September, 1942, ' 242 with a half-life of half a year. Sea­ B. B. Cunningham and L. B. Werner, borg, James, and A. Ghiorso later pro­ working at the wartime Metallurgical duced element 95 by first preparing Laboratory of the University of Chicago, Pu2-11, which decayed by beta emission isolated a few micrograms of PU239• Thus to an isotope of element 95 with mass plutonium became the first man-made ilUmber 241 and a half-life of slightly element to be produced in visible quan­ less than 500 years. tities. The names for elements 95 and 96 The realization that plutonium could were chosen with regard to their posi­ serve as a nuclear fuel like U2:'\ and tions in the periodic table according to the actinide concept. The corresponding that it might be made in quantity in a rare-earth elements are europium and nuclear chain reactor, resulted in man's first practice of alchemy on a production gadolinium, named in the one case for scale. Plutonium is the only synthetic ele­ Europe and in the other for J. Gadolin, a Finnish pioneer in rare-earth chemis­ ment yet made in kilogram quantities. try. Element 95 was accordingly named The huge plants at Hanford (and pre­ americium (Am) for the Americas, and sumably other plants considerably west element 96 curium (Cm) in honor of of Hanford) are devoted to this task-the Marie and Pierre Curie. solid embodiment of ideas which sound­ Both americium and curium have ed utterly fantastic a few years back. been isolated in a pure state by tech­ niques of ultramicrochemistry. Cunning­ Beyond Plutonium ham was the first to isolate visible amounts of americium. Using some iso­ After plutonium had been produced in quantity, the next higher elements, lated americium, it was possible to con­ vert an appreciable percentage to cu­ americium and curium, followed in rium in a pile. From this Werner and short order. Based on methods worked Perlman obtained the first curium in the out for producing neptunium and plu­ free state. The subsequent work with tonium isotopes, principally by cyclo­ pure americium and curium has pro­ tron bombardments of uranium, Sea­ vided abundant evidence for the similar­ borg and co-workers discovered ele­ ity of these elements to their prototype, ments 95 and 96 during 1944 and early actinium. 1945. The speed of discovery of these The elements so far discussed fill in elements was largely due to the accurate the periodic table completely from hyforecast of their chemical properties. ¥= _22_3-+' _2_2_4_-+--1_-i _ ! 2 1 23 3 23 2 � 29 1 2 3 0 3 -+ -+ __l_ __ __--_ -r __ _f- -+ _ __ __ 227 2 26 _ _ . _---; _ _ 2 28 23 4 -- __ . .. ..... ......... .. H . �_ • I. Perlman and G. T. Seab01'g are professors of c h e m istry at tIle University of Californ ia. 23 7 I 23 8 I em 238 ; . PU 234 23 9 " ". 24 0 24 1 _ 24 2 242 ;}. -;38 _ P�38 411"" ....-t------... b .. ",.!'".. ,. ... .-....---- , - ..--... j.. ... .....-... - j-...-.....--j---- ! · �Np 238 Np 234 i , ------- · _-========:===:=I ===:====:===::::_::===:===�== · ·· � :::::-",.:,······��U.�23��+·�',·.� 1 U 230 I ___ 1 drogen through curium. If any new ele · ments are to be added, they must lie above curium in atomic number. The beginning of 1950 saw the announce­ ment of the discovery of the first trans­ curium element, number 97, by S. G. Thompson, Ghiorso and Seaborg at Berkeley. In the naming of element 97, the same convention was used as for the preceding elements. The element in the rare-earth series that corresponds to ele­ ment 97 is terbium, named for Ytterby, Sweden, where extensive rare-earth de­ posits were found. It is therefore proper that the new element be called berkeli­ um (Bk), in view of the role played by the University of California at Berkeley in the preparation of most of the syn­ thetic elements. An isotope of berkelium was first pre­ pared by the irradiation of a minute quantity of americium with cyclotron alpha-particles. Isolation of its radio­ activity was accomplished in December, 1949, culminating four years of work on the problem. Further new elements doubtless can be expected. The difficulty of finding new elements in the transuranium re­ gion becomes increasingly severe, how­ ever, principally because it becomes less and less likely that isotopes can be prepared with sufficiently long half-lives to allow time for the intricate chemical separations. At what point more basic difficulties will arise cannot yet be said. .1 Pa "6 I � ! Pa�30 I�� __ _ __ and arrows ) hy transmuting natural isotopes into arti­ ficial ones with such methods as pile and cyclotron hom. hardment. These artificial isotopes douhtless existed in nature at one time. Isotopes that decay hy emitting an _ !"'"" �' ! . - ,. - -_-+__�__-+____ ��� �_ ,__v '� __ _ __ � � -== _ __ __ alpha particle lose an atomic numher of two and an atomic weight of four. Those that emit a negative heta particle gain an atomic numher of one; those that emit a positive heta particle lose an atomic number of one. 47 © 1950 SCIENTIFIC AMERICAN, INC There is little doubt that the averages of conditions which make up the weather have changed during the course of history. What about man's efforts to alter them further? by George H. T. Kimble CUMULUS CLOUDS shed rain on the arid earth of New Mexico. This aerial photograph was made on July 21 of last year after Irving Langmuir and his associates had sown the air with crystals of silver iodide (page 50). 48 © 1950 SCIENTIFIC AMERICAN, INC HE one point on which most peo­ ple agree when they talk about the weather is that things were very dif­ ferent when they were young: Beyond that, differences of opinion begin to creep in quite rapidly, for memory plays queer tricks with all of us where the weather is concerned. We tend to be ex­ ceptionally good at recalling certain kinds of weather, because of the effect they may have had upon our outdoor sports or our rheumatism, and excep­ tionally bad at recalling other kinds that did not happen to matter to us. What, exactly, is happening to our climate? Is it merely fluctuating on a short-term basis or is it undergoing a major long-term change? Some investigators have been at con­ siderable pains to show that the world's climate has rep1ained essentia.lly stable since early historical times. The late geologist J. W. Gregory argued convinc­ ingly that because the distribution of the date palm in the Levant was prac­ tically the same in Biblical times as it is today, the mean temperature of Pales­ tine has not altered materially. Others have argued that, because the olive can still be made to grow in North Africa near the margin of the desert, the cli­ mate has not deteriorated significantly since the days when the Roman settlers around Timgad carried on their highly profitable trade in olive oil. Moreover, it must be admitted that a change of land­ scape is no proof of a change of climate. The decay or disappearance of once­ proud cities that stood in areas now bar­ ren does not necessarily mean a decrease in rainfall; it may have resulted, in part at least, from overgrazing of the sur­ rounding pastures and the improvident use of the plqw. Soil erosion was an empire-killer long before the 20th cen­ tury. Nonetheless we do have evidence of marked changes in climate during re­ corded history. Consider the following three cases, taken more or less at ran­ dom. The first concerns the climate of Egypt. In the second century A. D. Claudius Ptolemaeus of Alexandria, who on all counts was one of the greatest geographers of antiquity, kept a system­ atic diary of the Egyptian weather. He had no thermometer or rain gauge, but he faithfully recorded thunderstorms, rainy days, winds and so on. From this record it is possible to reconstruct the main features of the climate of his day. The difference between 150 A.D. and 1950 A.D. could hardly be more striking. Nowadays Egyptian summers are rain­ less; then they had almost as many rainy days as the winters. Today thunder­ storms are unknown; then they were frequent in the hot season. Now the pre­ vailing, almost the only, summer wind is from the north; then it alternated with winds from the south and west. T The second illustration is even more two degrees have been general over the period of the last 100 years or so. dramatic. In the 11th century, almost 1,000 years ago, there was a flourishing More emphatic than the rise in mean Norse culture in Greenland. Its sagas re­ annual temperature has been the warm­ late that there were some 300 farmsteads ing up of the winter half of the year. At along the West Coast of the great island, Washington, D. C., during the 20-year period ending with 1892 there was a supporting 10,000 people and large numbers of sheep and cattle. This col­ total of 354 days with freezing tempera­ ony continued to lead an almost self­ ture during the spring months; for the 20 years ending with 1933 the corres­ supporting existence until the 14th cen­ ponding total was 237. At Montreal sub­ tury, when it appears to have fallen zero temperatures are now only half as on grim days. By 1400 A.D. very few common as they were 75 years ago, and settlements were left, and these were the mean temperature for March has fighting a losing battle. While we are risen more than six degrees. In Spitsber­ not going to suggest that the depopu­ gen the average December temperature lation of Greenland can be explained nowadays is more than 10 degrees higher solely in terms of climatic change, ar­ than it was 30 years ago! chaeologists have provided irrefutable The upward trend in temperature has evidence that the climate did undergo been accompanied in several parts of the a deterioration. There are ancient Norse graves in the southern part of the island, . world by a downward trend in precipi­ tation. Particularly noticeable has been with tree roots intertwined among the the decline in snowfall in parts of North bones, in soil that is now permanently America. At Montreal, for instance, the frozen. expectation now is not much more than The third illustration is taken from the 80 inches of snow in a season, as against British Isles. At the present time the 130 inches or so in the 1880s. Including summer season in England is not warm both snowfall and rainfall, the total win­ enough to ripen grapes except in a very ter precipitation (in terms of water) has few sheltered locations, and then only if declined from 22. 12 inches in the 1900s the summer is unusually hot. But at the to 19.80 inches in the 1940s. time of the Norman Conquest things These temperature and precipit�tion were different. The Domesday Book trends are far from being world-wide, mentions no fewer than 38 vineyards, in however. It is the Arctic, sub-Arctic and addition to those of the Crown, in Eng­ mid-latitude zones that have experienced land. In the 12th century vine dressers the major increases of temperature; the are frequently mentioned in abbey tropical and subtropical zones have be­ chronicles as forming part of the normal come a little cooler, if anything, in staff of an ecclesiastical estate. One the past half-century. The decline in William of Malmesbury, writing about precipitation has occurred chiefly in 1 150 A.D., assures us that the vale of North America, Africa, Australia and Gloucester "exhibits a greater number Brazil. of vineyards than any other county in Already some of these changes are England, yielding abundant crops and clearly reflected in human affairs. For of superior quality: nor are the wines instance, shipping operations in the made here by any means harsh or un­ White Sea and the Gulf of Bothnia can grateful to the palate, for in point of sweetness, they may almost bear com­ frequently be continued three to four weeks longer into the winter than for­ parison with the growths of France." A merly. In parts of Siberia the southern century later such references became boundary of the zone of permanently much less common, and by the end frozen ground is. receding poleward of the 14th century they had disap­ several dozen yards per annum. In peared almost completely. It would Northern Hemisphere waters various seem, then, that the English summers kinds of commercially valuable fish have were distinctly warmer during the 12th migrated northward. The common cod and 13th centuries than they normally now is found as far north as the 73rd are today. latitude off the West Coast of Greenland; E know for certain that important the cod catch off this coast amounted to 13,000 tons in 1946 as against five tons changes in the climate of the North­ in 1913. ern Hemisphere are going on at the On land the warming up of the cli­ present time. These are not merely short­ mate has begun to make itself felt in the term fluctuations. In Philadelphia the mean annual temperature has risen by acceleration of plant and animal growth and the poleward extension of various four degrees in a century-from approxi­ plant and animal habitats. In Iceland mately 52 degrees F. in the 1830s to over 56 degrees in the 1930s. In Montreal the_ there has been an extension of barley cultivation. The same is true of Norway, rise has been from 42 degrees F. in the 1880s, when observations began, to 44 where there has been a noticeable spread of farming up the sides of some of the degrees in the 1940s. In Spitsbergen the mountains. In Sweden, Finland, Alaska, rise since 1912 has been approximately and northern Quebec the coniferous for­ four degrees. In Scandinavia and the ests are growing faster and are beginBritish Isles rises of the order of one -to W 49· © 1950 SCIENTIFIC AMERICAN, INC NEW MEXICO TEST observers (right) watch thunder­ storm over a mountain range nine hours after "seeding" with silver iodide. Seeding began at 5 :30 a.m. First cloud appeared at 8:30; first cumulus cloud at 10:30. RIFTS APPEAR in a formation of stratus clouds after they are sown with dry ice crystals. The clouds were sown in a pattern of the Greek letter gamma. The rift in the right foreground is 20 miles long and two wide. 50 © 1950 SCIENTIFIC AMERICAN, INC ning to colonize new ground. In eastern Canada the northern limit of feasible cultivation for crops such as wheat has advanced 200 to 300 miles. Some farm­ ers in southern Ontario are even begin­ ning to experiment with raising cotton! We shall not concern ourselves here with the reasons for this climatic trend, except to note that in all probability long-term variations in the amount of radiant energy received by the earth from the sun have something to do with it. It is also worth pointing out, inci­ dentally, that the artificial heat of mod­ ern cities has a far from negligible effect on the local climate. Heat engineers have concluded that in a North American city the size of Montreal (1,125,000) the amount of heat escaping into the lower atmosphere from factories, offices and homes on some days could raise the air temperature by three to four de­ grees. HAT, if anything, can man do Wabout the weather today? It goes without saying that the changes we have mentioned are not pleasing to every­ body. The decline in winter precipita­ tion suits city street-cleaning depart­ ments, which have to clear the snow away, but the watershed engineers of North America are not nearly so happy about it. The smaller the snowfall over their catchment basins, the lower their water-storage reservoirs are likely to fall during the summer. This was dramat­ ically shown in the city of New York during the past winter, when the city was caught in a grave water shortage because of abnormally low precipitation. As a result the city fathers are investi­ gating the possibility of manufacturing rain by the cloud-seeding technique. Of course there is nothing very new about the idea of tinkering with the climate. The folklore of primitive tribes is rich in magic formulae for rain-mak­ ing. Around the turn of the present cen­ tury great interest developed in projects for controlling the elements. There were even international congresses on how to prevent hail from damaging crops. It was thought that a bombardment of storm clouds by gunfire might do the trick, but the only result achieved was a high accident rate among the scien­ tists! About the .same time the U. S. Government carried out a rain-making experiment in Texas. Balloons fitted with gas and dynamite were released under likely clouds. Admittedly a little rain did fall, but the Weather Bureau, on examin­ ing its charts, said it would have rained anyway. Since then there have been plenty of other novel suggestions as to how the weather might be controlled in a given particular. Prior to 1939 most of them went into the wastebasket. During the war, however, several such devices got a trial. One .was a new technique of fog dispersion used at airfields: the burning Hawaiian Islands in September, 1947, a of gasoline vapor, sprayed through per­ cumulus cloud below the freezing level forated pipes that were laid along the was seeded with dry ice. This cloud edges of the runways, generated intense commenced to precipitate within 10 heat which evaporated the moisture in minutes, and rain fell continuously from the air and so "burned" off the fog. But it for several hours before the cloud the cost was terrific: the gasoline con­ reached the freezing level. sumed amounted to an average of 6,000 As the physicists have since discov­ gallons per plane per landing. ered, a number of conditions have to be Certainly the most interesting of the satisfied before rain may be released new ideas is the cloud-seeding method from a cloud simply by seeding it with for making rain, the development of dry ice or silver iodide. In the first place, the cloud must be at least 4,000 feet which is said to have been stimulated originally by the possibility of its use as a deep, and dense enough to contain a weapon. (It does not require a very live­ large number of water drops; thin stratus ly imagination to picture the havoc that or strato-cumulus clouds will not do. could be wrought upon a nation unlucky Secondly, the temperature and wind enough to have its clouds dehydrated by conditions must be just right to maintain an enemy situated to windward!) What turbulence in the cloud. Thirdly, and is the theory behind. the technique, closely related, the vertical velocities and what results have been achieved to within the cloud must be appreCiable; in date? the case of a cloud that does not pene­ According to one modern theory about trate into the freezing zone they should precipitation, the formation of rain in a be of the order of 15 to 20 feet per sec­ cloud requires the presence not only of ond. If the rain is to be stimulated by water droplets but also of ice crystals. (collisions of supercooled waterdrops and Thus clouds situated below the freezing ice crystals, the cloud must extend sev­ level of the atmosphere cannot form eral thousand feet above the freezing rain. So the idea naturally suggested it­ level. Such a combination of atmos­ self: why not provoke such clouds to pheric conditions probably is rare except precipitate their moisture by supplying in a cloud that is already on the verge ice crystals artificially? Such crystals, it of precipitating. Indeed, some physicists was argued, should grow like seeds in have gone so far as to suggest that in every case where rain or snow fell after fertile soil, and it would be only a matter of time before they would be big enough seeding, the state of the atmosphere was to overcome any updrafts and so force such that the precipitation would have their way down to earth. The theory was occurred in any event. It is evident, therefore, that the tech­ first put to the test by the U. S. physicist Irving Langmuir and his associates on nique is unlikely to be of any assistance November 13, 1946. Six pounds of in helping to break a drought, for most granulated dry ice were "seeded" into a of our prolonged dry spells are asso­ ciated with anticyclonic conditions four-mile stretch of supercooled strato­ cumulus over Massachusetts. A few min­ which seldom yield clouds of any depth. The same objection applies to the view utes later light snow was seen falling out that countries of low rainfall, like Aus­ of the cloud, but so far as could be ob­ served none reached the ground. Other tralia, can be given a new climatic deal. experiments followed in fairly quick suc­ E. G. Bowen of the Australian Council cession. One of the most spectacular took· for Scientific and Industrial Research has place in Australia. A large cumulus categorically declared that "it will be cloud, one of many nonprecipitating quite impossible to do anything for the clouds in the sky at the time, was in­ desert areas by this method; the right duced to produce rain and to grow into types of clouds do not exist there in suf­ ficient quantity." a cumulo-nimbus cloud extending al­ most 20,000 feet above the other cloud HE seeding technique holds out tops. This cloud continued to yield show­ other useful possibilities, however, ers throughout the afternoon. Another which should not be overlooked. The experiment in New Mexico iri the sum­ mer of 1949 produced a much heavier seeding with dry ice of a large uniform rainfall. Nevertheless the results of the stratus cloud which is bel<�w the freezing experiments in general have been incon­ point is capable of dissolving the cloud clusive. Of the dozens of tests made in -sometimes temporarily, often perma­ many different parts of the world, only a nently. Obviously this treatment might few have produced convincing amounts be turned to good account, particularly of rain. In a series of 45 seeding experi­ in winter, when anticyclones are fre­ ments over Hawaii only one yielded rain quently accompanied by a stratiform cloud cover that produces dull, depress­ of any duration. It seems that the crystallization theory ing weather and sends up the daytime is not quite satisfactory. Surprisingly consumption of gas and electricity for lighting. Some of the experimenters hold some of the best results have been ob­ tained in clouds where ice crystals could that many of our worst winter fogs could be dissipated simply by scatter­ have played little if any part in the for­ mation of the rain. For instance, over the ing a few handfuls of dry ice or other T 51 © 1950 SCIENTIFIC AMERICAN, INC Our Industrial Resea rc h TeaJlJDl Is organized to accom­ plish the profit-motivated aims . of industrial re­ search. 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This issue, which will be sent to you FREE with this special offer, covers 44 Chemical, Drug and Liquor Stocks including: Abbott Labs. Amer. Home Prod. Bristol- Myers Gillette Lambert Company Lehn & Fink Mead Johnson Parke. Davis Rexall Drug Sharpe & Dohme Sterling Drug American Cyanamid Dow Chemical Du Pont Eastman Kodak Hercules Powder Monsanto Chern. Anheuser Busch Schenley Hiram Walker FREE: !� �� ::�; t� :�� �: ���: iS p l I at no extra cost. Special Offer. $5.00 n 5 a as part of this INTRODUCTORY OFFER (New subscribers only) includes 4 weekly editions or Ratings and Reports-covering 177 stocks in 14 industries. It includes also a Special Situations recommendation, Super­ dsed Account Report, 2 Fortnightly Letters and 4 '''eekly Supplements. (Annual sub­ scription $95.) Plus the Chemical {51 Drug Stock Issue Jree. Send $5 to Dept. SA·I. VALVE LINE lnvest.nent Survey Value Line Survey Building 5 East 44th St .• N. Y. 17. N. Y. ARNOLD BERNHARD & CO., INC. WATER VAPOR is supercooled in a tank during laboratory experiment in precipitation by dry ice crystals. VAPOR CONGEALS into a curious pattern after the tank has been sown with a few crystals of the dry ice. foreign particles into a supercooled ground fog. Vincent Schaefer, an associate of Langmuir and one of the chief pioneers in this field, has recently said that the seeding technique may well prove to be more efficacious in making it disintegrate a storm cloud than in precipitating it. In this way many a valuable fruit crop might be saved from a disastrous hail or rain storm. Schaefer also believes that it may be possible to eliminate, or at least to reduce, the icing hazard to aircraft by patrolling airline routes with scout planes and seeding dangerous clouds to disperse them. Others are of the opinion that similar "interference techniques" might be successful in combatting the hurricane and tornado menace. . Suppose for the sake of argument that physicists and technologists are eventually able, by one means or an­ other, to effect a radical change of cli­ mate: Ought we to allow them to do it? It appears to me that there are at least two reasons why we should be slow to give them their head. In the first place, the results would be very difficult to fore­ cast; they might be the opposite of what was intended. There are too many un­ knowns in the atmospheric equation. In the second place, even if a given opera­ tion was successful, the outcome would be sure to please fewer people than the weather we have come to expect. A big freeze might gratify the winter sports enthusiasts of Lake Placid, but not the hotel keepers of Palm Beach. One farm­ er might decide he wanted to manu­ facture rain for his grain, while his neighbor wanted sunshine for his straw­ berries. Surely the world has enough troubles on its hands at the moment without spawning more! other snappy sports for the rich transients who had tired of playing with slot ma­ chines. Apparently the plan worked beautifully-until the people in the neighboring state of Utah got wind of what was happening. The farmers of the Mormon state, who depend upon snow­ fed streams that flow down from the lofty Wasatch Mountains, naturally take the greatest interest in the year-to-year vari­ ations of the winter snowfall on these mountains. Noticing that the mountains did not seem to be accumulating snow at the normal rate, they sent a surveyor up with a foot-rule. He reported that there were only 40 inches of snow up there instead of the usual 60 or so. This could mean only one thing: the wicked Nevadans had tampered with the course of nature and diverted the snowfall to their side of the mountains. Now there is the making of a first-class legal battle between the two states, for the Utahans have unearthed a law in the statute books making it illegal to divert water. The lawyers of Reno, experienced as they may be, will have their work cut out to prove that the snow in those diverted clouds did not contain wa­ ter! Since the lawyers started to take this rain- and snow-making business in hand, the enthusiasm of many of its erstwhile supporters has flagged. In Canada the mere threat of legal action by farmers, foresters and other interested parties was enough to put a stop to all cloud-. seeding operations for a time, while in the U. S. it constrained one of the in­ dustrial companies that had pioneered the technique to cease all o�tdoo.r ex­ periments. This is not to say that we must or ought to leave the world's weather ex­ actly as we find it, for in some respects it has deteriorated as a result of human folly, while in others it can easily be "touched up" to the advantage of all. Many a fruitgrower, for instance, owes his prosperity to the smudge-pot or or­ chard heater, which enables him to ward off untimely frost. The planting of shelter E have recently had an eloquent W demonstration of the troubles that arise when men suspect their neighbors of tinkering with the weather. The peo­ ple of Reno, Nev., decided they would like to anoint the slopes of nearby Mount Rose with snow to provide skiing and 52 © 1950 SCIENTIFIC AMERICAN, INC • tank. Experiment was performed in the General Electric laboratories. belts has had similarly beneficent re­ sults for the life. and economy of many a Midwestern farmer. Not only do the trees give shade to animals and men; they also break the force of the wind, anchor the snow and retard the rate of evaporation of ground water, thus con­ serving moisture. There are indications that the construction of great water­ storage reservoirs in the Sudan, the Pun­ jab and the U. S. West has reduced the extremes of summer heat and winter cold in. the nearby regions, and in the long run it may possibly increase the rainfall. A striking illustration of the measure of man's power to change his climatic environment, in this case for the worse, is evident in a part of the mountain country of Tennessee. There in the Cop­ per Basin is an area of 7,000 acres that was once heavily forested but has now been completely denuded by smelter fumes. Weather observations taken at different stations show that during both winter and summer the average daily temperature in this blighted area is three to four degrees higher than in surround­ in'g lands still covered with forest; that the average wind velocity in the de­ nuded area is seven to 10 times as great in winter and 30 to 40 times as great in summer; that evaporation is twice as great there in winter and seven times as great in summer, and that the annual. precipitation is some 28 per cent great­ er in the forested than in �he open area. Somewhere in all this there must be a moral. This much at least seems clear: scientists and technologists are likely to add far more to the sum-total of human happiness by restoring the lost equili­ brium between earth, air and water than by attempting to produce a new one of their own contriving. - George H. T. Kimble is profes­ sor of geography and director of the meteorological observa­ tory at McGill University. The PANPHOT combines permanently aligned microscope, camera and light source in one convenient un it . The ofki4 Panphot Universal Camera Microscope Only the Leitz PANPHOT enables you to switch from micro­ scopic observation to photo-micrography without moving from your chair, for it's the only universal camera microscope with operat­ ing parts for both functions right at hand. Changeover from one to the other is fast, simple, dependable. Now available to industrial and technical laboratories, the PANPHOT is a perfect combination of research microscope and reflex camera. The PANPHOT permits the use of transmitted light, reflected light, darkfield illumination and polarized light. The permanently aligned light source provides a filament lamp for observation and an arc light for photo-mIcrography. Easy observation of the image to be photographed is provided by a large ground glass in the reflex mirror camera. The camera ac­ commodates 3;4" x 4;4" plates or cut film for black and white or color work. A full range of accessories is available to equip the PANPHOT for every phase of photo-micrography, photo-macrography and for drawing and proj ecting micro-images. Write to d a y for information to Dept. SA E. LEITZ, Inc., 304 Hudson Street, New York 13, N. Y. LEITZ MICROSCOPES. SCIENTIfiC INSTRUMENTS LEICA CAMERAS AND ACCESSORIES 53 © 1950 SCIENTIFIC AMERICAN, INC ""SOCIAL INSTINCTS" It is too often assumed that the law of nature is: kill or be killed. Presenting an argument for the opposite principle: a natural law of cooperation by Ashley Montagu Now this is the Law of the Jungle-as old and as true as the sky; And the Wolf that shall keep it may prosper, but the Wolf that shall break it must die. ... the strength of the Pack is the Wolf, and the strength of the Wolf is the Pack. -Rudyard Kipling T is curious that generally "the law of the jungle" has come to have an entirely different meaning from the one Kipling suggested. Most people would say that the rule of the jungle is: kill or be killed. Rugged individualism, aggressiveness, warfare-these have been thought to be the natural tendencies throughout the animal kingdom. Kip­ ling's sentimental verses suggest that, on the contrary, the law of the jungle is not the law of tooth and claw but the very opposite-cooperation. And strangely enough a great deal of modern research in various sciences indicates that Kip­ ling was right. Through many laboratory experiments and observations in the field we are being shown that we have been close to 100 per cent wrong in thinking of animal life as a dog-eat-dog existence. The truth seems to be that nature ad­ heres to the principles of the highest I ethics: the Golden Rule is sound biology. This concept is so far-ranging in its implications for human beings and for nations that a long-term research pro­ gram has been started to collect and syn­ thesize pertinent data from all parts of the world. The sponsor of the project is the Foundation for Integrated Educa­ tion, a recently organized group of scholars and businessmen. Examples of cooperation in the animal world are not at all difficult to find, and they turn up in the most surprising places. Take the case of African ele­ phants, which are notoriously savage and resistant to taming. Hunters in Africa have seen elephants stop beside a wounded comrade and laboriously lift him with their trunks and tusks, when the so-called law of self-preservation should have made them run to safety. The noted explorer Carl E. Akeley sev­ eral times saw threatened herds of ele­ phants gather in a ring, with the younger and huskier beasts forming the outer circle to protect the older ones. Or consider chimpanzees, traditional­ ly regarded as self-centered little crea­ tures. Workers at Yale University's Yerkes Laboratory of Primate Biology in Florida have seen chimps helping each other carry loads and even passing food to one another through the bars of their cages. Even so lowly a mammal as the mouse is known to cooperate with its fellows. A Polish experimenter named T. Vetu­ lani found that white mice isolated in separate cages failed to grow as fast as those that were grouped two, three or four in a cage. The grouped mice hud­ dled together and kept each other warm, thus conserving energy for growth, and they also healed one another's sores by licking. At the University of Chicago the zoologist W. C. Allee and his co-workers have discovered tendencies toward mu­ tualism among goldfish. For example, a young goldfish will grow more rapidly in water that has previously been inhab­ ited by another goldfish than in clean, uncontaminated water. The reason is that the second fish feeds on food re­ gurgitated by the first. Allee made a systematic investigation to determine whether animals survive a catastrophe better in a group than singly. The most interesting of several experi­ ments on this problem involved planar­ ian worms. The catastrophe was ultra­ violet radiation, which is deadly to these animals. The worms were arranged in Petri dishes, the experimental animals BASS are frequently cannibalistic when they live alone. . er bass (left). Bass in ponds cleared of vegetation, how­ Bass isolated in weedy ponds were observed to eat smallever, swam in groups and eschewed cannibalism (right). 54 © 1950 SCIENTIFIC AMERICAN, INC being crowded 20 to a dish and the con­ trol animals isolated one to a dish. The worms were then irradiated. All the worms died eventually-but the crowded worms hung on to life much longer. In one test they lived an average of 517 minutes after radiation, while isolated worms lived only 41 minutes. One possible explanation is that the crowded worms tended to shade one an­ other from the lethal radiation. But that is not the whole story, as was proved by another experiment. This time all the worms were irradiated in groups of 20; none was isolated until after the damage had been done. Then 10 worms were taken from each group and placed singly in separate dishes, while the other 10 were left together. Again the grouped worms lived much longer than the iso­ lated ones, surviving an average of 148 minutes to the latter's 78. The worms that werc togethcr somehow lent strength to one another. How? Whatever the factor is, it has not yet been identi­ ned. LLEE and other investigators have A found that this rule of strength in numbers holds true practically every­ where they have looked. For example, a sea gull breeds more young when it lives in a large flock than in a small one. A salamander tadpole whose tail has been cut off will regenerate it more rapidly when other tadpoles are in the tank than when it is alone; the probable explana­ tion is that the presencc of several tad­ poles raises the salt content of the water to approximately that of the cut surface and thus favors growth. An ant digging a nest moves more dirt when it works in the company of other ants than when it works alone. The spermatozoa of the sea-urchin retain their ability to fertilize eggs much longer il1 a heavy concentra­ tion than in a diluted onc. And so on; the examples can be multiplied. But all these examples deal only with cooperation among animals of the same species. v"hat of the so-called warfare between different species? Lions kill zebras-no question about that. But the lions do it only for food. This type of aggression can no more be considered war than man can be said to war on oysters and chickens. Lions do not kill for sport or out of blood lust; they kill only when hungry. African explorers have seen them trot through herds of easy game without making the slightest attempt to attack. Surely cats and rats are instinctive enemies! Actually they are not: a cat has to learn to kill rats. A Chinese in­ vestigator named Zing Y. Kuo raised three groups of kittens under different conditions. Group A were left with their mothers, and from the first days of life saw how rats were killed. Group B were not allowed to see killing until they were several months old. Group C never saw killing at any time, and were raised in the same cage with baby rats. The up­ shot was that in Group A 85 per cent of the kittens became rat killers; in Group B only 45 per cent killed rats; in Group C the kittens lived in peace with their rat cagemates and all other rats of the same species. Kuo concluded: "If one insists that the cat has an instinct to kill the rat, I must add that it has an instinct to love the rat, too." The traditional belief in "hereditary enemies" among animals is constantly being refuted by the Sunday supple­ ments, which dote on printing pictures of dogs that have adopted cats, and tame foxes that play with chickens. The Phila­ delphia Zoo has witnessed some remark­ able examples of such friendships. There a cat and a Senegal parrot became so attached to each other that they slept together. Another cat struck up an ac­ quaintance with a deer, and chose the deer cage to have her kittens. The deer took special care not to step on the litter. A female goat was cautiously introduced by the zookeepers to a female black rhinoceros, a creature of very savage PLANARIAN WORMS survive longer in groups than alone. In one series of experiments the worms were temperament. The rhino, instead of at­ tempting to eat the goat, befriended her. The two were inseparable for the rest of their lives. ERHAPS the most remarkable story Pof the effects of companionship comes from the Ohio Bureau of Fish Propaga­ tion. The Bureau chief, T. H. Langlois, has persuaded the bass in the Bureau's rearing ponds to give up cannibalism-a practice long supposed to be instinctive with these fish. Langlois noticed that if bass are put into weedy ponds, they tend to become separated by the vegetation and fail to form large social groups. Some of the fish take up lodgings in se­ cluded spots and apparently develop a gangster psychology. Any small outsider unlucky enough to stray into these re­ stricted territories gets eaten. The can­ nibalism does not stop when other food is thrown into the water by the fisheries men. The gangsters either fail to see the food because of the intervening vegeta­ tion, or are just not interested. Langlois' solution was simply to clear the vegeta­ tion out of the ponds before stocking them with bass. Now all the fish had to mingle. When food was thrown to them, they all ate together. With everybody well feel and 'everybody acquainted with everybody else, nobody tried to eat any­ body. These examples and scores of others recorded by scientists in many parts of the world emphaSize how strong and deep-seated is the urge toward social life and mutual aid throughout .animal life. What is the basis of this urge? The an­ swer proposed here is that the social na­ ture of all living things has its origin in the relationship between offspring and parent-the fact that the one is for a time dependent on the other. This hypothesis appears to bind together a large mass of facts not previously known to be related. Consider a unicellular organism, the amoeba. v"hen the amoeba reaches a certain size, it can avoid death only by plac � d in dishes and exposed to ultraviolet radiation. The more worms in the dish, the longer thcy survived. 55 © 1950 SCIENTIFIC AMERICAN, INC dividing. Its continued existence is de­ pendent on the proper formation of the daughter cells, and their existence in turn is dependent on the proper func­ tioning of the parent through the various stages of mitosis. Here is a real instance of interdependent, social life; it exhibits in miniature the pattern of cooperative behavior that we see throughout nature. Cooperation is the mechanism by which every new individual is formed, whether sexually or asexually. Cooperation is the means by which it keeps alive through the first precarious stages of existence. Cooperation is as basic to its nature as are irritability and motility. Let us consider our theory in terms of man. In the first weeks of life the human infant appears solely concerned with sat­ isfying its physical needs, such as food and warmth. But gradually its feelings of satisfaction are transferred to the per­ son or persons who make the satisfac­ tions possible. From then on the baby is not content with merely getting enough to eat; it also needs a close emotional connection with the provider-the moth­ er or mother-substitute. It cannot live by bread alone. Thus the mutuality that governed the infant's life in the uterus is raised to the psychic level. The baby now has a social "inclination." This characteristic can never be thrown off; it is too closely interwoven with the in­ dividual's firsf encounters with the sur­ rounding world. This is the pattern in which every adult human being is molded. There are no exceptions; infants who do not go through these stages, who are not cared for or "mothered," do not survive. Hence we may infer that what the human be­ ing desires most of all is security. He wants to feel related to something, whether to family, friends or deity. Man does not want independence in the sense of functioning separately from the in­ terests of his fellows. That kind of inde­ pendence leads to lonesomeness and fear. �lhat man wants is the positive freedom that follows the pattern of his life as an infant within the family-de­ pendent security, the feeling that he is part of a group, accepted, wanted, loved and loving. In human beings who develop nor­ mally, this feeling of love and unity with the group continues to grow all through life. It is a common observation that the happiest persons are those who most strongly feel a sense of connection with the whole community. They are happiest because they are giving fullest play to their innermost tendencies. Thus we reach the conclusion that the ethical idea of love is no artificial crea­ tion of philosophers but is rooted in the biological structure of man. To love thy neighbor as thyself is not only religion's edict but nature's as well. Men who act in disregard of this principle are actually warring against their own bodies. The result is bound to be havoc for them­ selves and for those around them. ERE is a conclusion fraught with Hgreat significance for mankind. It gives support to all forces that are at­ tempting to weld men closer together and so to increase the quantity of secur­ ity for all individuals. It turns the weight of science against all advocates of sepa­ ratism, isolationism, aggressive individu­ alism. It brands the theories of the hate­ mongers not merely as immoral but as unnatural. If this conclusion were wide­ ly propagated, it might help strengthen the average man against the appeals of ultranationalist demagogues. Now it must be acknowledged that the opposite conclusion is deeply rooted in modern thinking, and that a seeming­ ly powerful objection may be offered to our theory. This objection derives from what people suppose to be the Dar­ winian scheme of evolution. If the dom­ inant impulse in all animals is coopera­ tion, if man's biological structure is rooted in love, what becomes of Dar­ winism? What about "the struggle for MICE also exhibit the benefits of social behavior: One experimenter found that white mice alone in a cage existence," "natural selection," "the sur­ vival of .the fittest"? The answer is that these conceptions are only one side of the picture. Cer­ tainly aggressiveness exists in nature, but there is a simultaneous drive toward cooperation. And the evidence strongly indicates that the latter is the stronger and biologically the more important. For if struggle and conflict had dom­ inated life back to its very beginnings on this planet, how would unicellular ani­ mals ever have joined forces to produce the first multicellular creatures? Without cooperation, evolution as we conceive it could never have started. Furthermore, the coexistence today of so many differ­ ent species of animals throughout the world is sufficient testimony to the ex­ istence of a principle of mutualism, tol­ erance, live-and-Iet-live. It is a narrow interpretation of Dar­ winism, indeed a perversion of it, that has given rise to the belief that combat and conquest are nature's whole plan, and that as a consequence rivalry, ag­ gression and imperialism are the inevita­ ble way of personal and social life. Actually Charles Darwin's own attitude was altogether different. He appreciated the powerful role of cooperation, and made this clear in The Descent of Man. In a passage to which his diSciples have given too little attention he said: "As man advances in civilization, and small tribes are united into larger com­ munities, the simplest reason would tell each individual that ,he ought to extend his social instincts and sympathies to all members of the same nation, though per­ sonally unknown to him. This point be­ ing once reached, there is only an artifi­ cial barrier to prevent his sympathies ex­ tending to the men of all nations and races." • Ashley Montagu is professor of anthropology at Rutgers Univer­ sity and author of On Being Hu­ man, to be published this month. failed to grow as fast as those grouped two, three and four in a cage. The mice also licked each other's sores. 56 © 1950 SCIENTIFIC AMERICAN, INC BUSINESS IN MOTION Because everybody spends a lot of time indoors, masonry construction. The flashing is of chief interest under a roof of one kind or another, the building to those designing and building large commercial industry has always been of prime interest to Revere. structures, though of course it is also applicable to There are two reasons for this concern. One is the the private homes built of brick and stone. There obvious consideration - a good, weather-tight, long­ is now available thru-wall flashing for economical lasting building should contain adequate amounts of and enduring protection against seepage and leaks sheet copper in the appropriate places. The other is at copings, parapets, belt courses, sills, spandrel beam our feeling that, as.a leading producer of sheet cop­ facings and similar masonry applications. There is a per, we have an obligation to the public to see that reglet and reglet insert, also of solid copper, for water­ there is an understanding of the economy and satis­ proofing spandrels at costs comparable with or less faction obtained through the correct use of this metal than mopped-on waterproofing. There is vertical rib for waterproofing. siding for use on high parapet walls, penthouses, and Hence Revere some years ago embarked upon an so on. All these items are pre-formed, and the simple extensive program aimed at devel­ directions for their use can be easily oping principles, followed by any contractor, builder, specifications and designs for suc­ or sheet metal worker. These new the engineering cessful application of sheet copper Revere Copper Products are avail­ to all types of buildings. The in­ able through sheet metal distribu­ formation thus obtained has been tors throughout the country. freely published for all to follow, Though we have given these new with assurance of lasting protec­ items the widest possible publicity, tion, whether for a home or a hos­ we realize that in thfs vast coun­ pital, an office building, hotel or try it is unlikely that absolutely factory. Though anybody's copper everybody concerned will l earn can immediately about them and how be used according to these much they can add to true economy. specifications and designs, naturally Revere hopes it will be Revere copper, and indeed It takes time for news to get around. This time­ we are getting our share of the business. It is a great lag is a problem for every company offering a new satisfaction to us not only to sell the copper, but to service or product. Recently we saw an advertise­ ( felt ) know that it is being applied in such a way as to give ment of an important industrial material economical, enduring protection. This is esp�cially which it was suggested: "Write us what you make, in important in these days of high labor costs, which and benefit by our constructive ideas." That is good make repairs due to the use of inferior materials or advice. Revere therefore recommends that no mat­ improper installation cost so much more than the ter what you buy, whether metals or felt, chemicals price of good materials and workmanship, if used' in or plastics, building materials or containers, you the first place. give your suppliers the opportunity to collaborate Now Revere has expanded its service to the build­ ing trades by offering solid copper flashing for with you on the selection and application of new as well as old materials. REVERE COPPER AND BRASS INCORPORATED Founded by Paul Revere in 1801 Executive Offices: 230 Park Avenue, New York 17, N. Y. 57 © 1950 SCIENTIFIC AMERICAN, INC The Probability of Death It varies considerably with age' and species. Man, however, has manipulated his curve of survival so it rather resembles that of the starved fruit fly by Edward S. Deevey, Jr. N I a world where the only certainties are death and taxes, and where even taxes can sometimes be avoided, how certain is death? There can be no doubt that .this question has been asked since earliest times, when men painted the bodies of their dead kinsmen or provided them with goods for the journey to the hereafter. From poets and philosophers we have had melodious answers to the question-defiant, anguished, acquies­ cent or exultant according to the au­ thors' personality and culture. From science, as we have come to expect, we get a statistical expression, not of cer­ tainty but of probability. How probable, 'then, is death? At birth the probability of death at the end of the life span is of course 1, but this is not exactly helpful. To know the proba­ bility of death at any given age, one needs to observe the mortality of a popu­ lation, substituting the universality of averages for the chancy behavior of in­ dividuals. Actuaries, on whose skill depends the whole ingenious procedure by which in­ surance companies convert the proba­ bility of death to the certainty of making a profit, have devised a handy scheme for expressing the facts of mortality. Their "life tables" become rather com­ plicated, but the principles on which they are constructed are not difficult to understand if we deal with a population of experimental animals instead of a hu­ man population whose members were born at various times. . A group of fruit flies is allowed to be born in the usual half-pint milk bottle, and a daily census is taken until the last survivor is dead. The "raw data" then give the number of deaths, d, at any age, x-which is written dx. We convert this figure to a percentage of the total original population. At any given time the percentage of deaths, subtracted from 100 per cent, gives the percentage of survivors, Ix. When the survivorship column of the life table is graphed, we can see at a glance the pattern of fruit­ fly mortality. Thus if we assume that the initial population had 100 members, those dying in their first day of life leave 100-d1 =11 survivors, those dying in their second day leave ll-d2=12 sur­ vivors, and so on until on the nth day the last survivor dies and In-1-dn=0. The mortality rate at any age (qx) is the ra­ tio of those dying during the given day to those alive at the beginning of that day: qx=dx/lx• Instead of taking a day as the time unit, we can of course use any interval, such as a year or a decade, but for accurate results the age intervals must be short in relation to the total life span. If survivorship is graphed on a loga­ rithmic instead of an arithmetic scale, so that a straight line represents equal rates rather than equal amounts of de­ creasing survivorship, qx can be read directly from the graph. Other columns of the conventional life table are derived almost as simply from one or another of these values. In particular, if one were to sell insurance policies to fruit flies, one would need to know the expectation of life (ex), better described as the mean subsequent life span. It is easy enough to perform this kind of manipulation on data from any labora­ tory population, and the comparative mortality of lower organisms is full of interest for the student of man, as com­ parative studies usually are. The rate at which organisms die expresses the bal­ ance between the tendency of their cells and tissues to maintain their organization and the relentless hostility of the world in which they exist. In other words, the survivorship curve of a population is a mathematical life line, recording in its sinuosities the contest between physiolo­ gy and environment which we call life­ and which Herbert Spencer defined as "the continuous adjustment of internal relations to external relations." . A famous essay by Raymond Pearl and John R. Minei' pointed to three distinct types of life curve: 1) Some animals, such as the mildly organized Hydra, ap­ pear to die without regard to age; no one age is more exposed to risk of death than another, and the Ix curve is a straight line. 2) Under special circum- 58 © 1950 SCIENTIFIC AMERICAN, INC stances, as when adult fruit flies are given no food but are granted a barely sporting chance to show their tenacity of life, they live their few allotted hours to­ gether and die almost simultaneously. 3) More usually an organism, typified at the extreme limit by so insecure a crea­ ture as an oyster or a dandelion, runs a heavy risk of death in infancy, but the few survivors to advanced age die at low and comparatively constant rates. HAT of man's mortality? Is it like or is it completely flexible, varying from type to type according to circumstances? How far can man control his own sur­ vival? To appreciate the answer it is im­ portant to realize that the evidence is not so easily gathered as it would be if men were born all at once at the will of some supreme experimenter. Under the con­ ditions in which men live and reproduce, the facts of death relate to individuals born at various times. and places in the past. To calculate a rate of mortality it is necessary to know not only the ages of those dying but the number alive at any age and exposed to the risk of death. Thus the basic datum of the human life table is not dx but qx' Such data are obtained from censuses and from bmeaus of vital statistics. When they are cast up, they do not de­ scribe the mortality of a defunct popu­ lation, as in our experiment with fruit flies, but instead predict the future mor­ tality of a hypothetical group. The mem­ bers of this group are imagined as born within the year of the census and ex­ posed throughout their lives to death risks at particular ages equal to those observed for those ages in the year of the census. Insurance companies have not failed to note that any general im­ provement in health as time goes on is a guarantee of profit, for the longer the average policyholder lives beyond the age at which he was expected to die, the more premiums he pays-at least in the case of "ordinary life" insurance. Cus­ tomarily such profits are shared with the policyholders, but it is a fact that until Wthat of Hydra or of an oyster, J 948 all American insurance premiums were calculated OIl a life table worked out in 1868. The human survivorship curve dis­ plays a remarkable sinuosity, corre­ sponding to real variations in the chances of death according to age. Mortality is relatively heavy in the first years of life, especially so in the first week and month. Beyond age 4 the modern American child has an excellent chance of living to maturity. Throughout middle life sur­ vival ratios are high and rather constant. As old age approaches the rates of mor­ tality begin to increase more sharply, but in extreme age, beyond age 90, it ap­ pears that one has almost as good a chance of living an additional 10 years as at age 80. This part of the curve is inevitably based on inadequate informa­ tion, but assuming that its form is cor­ rect, it recalls that of an oyster from ma­ turity onward, when the period of most excruciating hazard is over and a tiny fraction of survivors live to become liter­ ally superannuated. The curve as a whole shows a kind of oscillating compromise among the theo­ retical types of Pearl and Miner: In in­ fancy man is a little like the oyster or the mackerel; in childhood, when mor­ tality rates are decreasing, a temporary approach is made to the "rectangular" curve of starved fruit flies; in the middle years the constant risk of death resem­ bles that of Hydra; in old age man comes once more to imitate the oyster. Probably other mammals in a state of nature have life curves much like man's. Of the few for which data are at hand the one that most resembles man's is that of the big­ horn sheep of Mount McKinley, which in extreme youth and in old age appear to be especially likely to fall prey to wolves. It must. not be forgotten that this human survivorship curve represents a hypothetical modern population. To judge the extent to which the life span may be modified, it is necessary to con­ sider other groups of other times. Though we cannot easily look far forward, we can look backward. vVe see then a remark­ able thing: in the so-called Western countrics in general, and the U. S. in par­ ticular, the average length of life has in­ creased in spectacular fashion. Between 1838 and 1844 the expectation of life at birth of a male born in England was 40.19 years; a century later, in 1937, it was 60.18 years. The life span of the men of Massachusetts rose from 38.3 years in 1850 to 63.3 in 1939-41. Since 1900 in the U. S. as a whole the average life span has risen from about 48 to about 63 years. In short, the average length of life has nearly doubled in a century. But it is important to remember that this gain has come only in the average, which is de­ pendent on the general level of public health, i.e., on the physical and social environment. There is no evidence that the oldest people are living to greater ages than before; the maximum length of human life appears to be fixed at about 115 or 120 years. TOMBSTONES CURVES of survival for several organisms are plotted on the basis of survi­ vors pel' thousand (vertical coordinate) and age in relative units of mean life span (horizontal coordinate). Most oysters die in infancy; most starved fruit flies in old age. Death rate of Hydra appears to bc thc same at all ages. provide accurate data on the life span of man in Ro­ man times. Birth dates were carefully preservcd for astrological purposes. F the upper limit of age is determined I by man's genetic constitution, ob­ viously the elimination of all environ- mental caus'es of death, such as disease and accidents, would yield a population whose every member lived to about the same age. The survivorship curve would become a rectangle even sharper than that of starving fruit flies; birthdays would no longer warrant congratulation, and at age n-l (114 years?) people would start to dispose of their belong­ ings. But you and I will probably not enjoy the dubious pleasures of that day. The recent improvement of man's al­ lotted term of years is almost entirely the result of a concerted attack on deaths in infancy and childhood; the ills attend­ ing old age have scarcely begun to at­ tract medical attention. "Death from old age" is a legal fiction, not a medical fact, but it is deeply in­ grained in our thinking, even among physicians. Geriatrics has a long way to go to match the triumphs of pediatrics. That the infant science of aging is due for a boom is certain, if only as a matter of social justice. Partly because of de­ clining birth rates, and partly as a result of the greatly increased mean life span, the proportion of U. S. people over 65 rose from 2.6 per cent in 1850 to 6.8 per cent in 1940; by the year 2000 it should approximate 13 per cent. Thus the U. S. as a whole is fast approaching the pecu­ liar situation of southern California, where political and moral pressure is strong to "do something for the aged." Whether anything can actually be clone for the oldsters beyond providing them with more elderly companions is a question that cannot be answered, for it hinges on the unsolved problem of the 59 © 1950 SCIENTIFIC AMERICAN, INC AVERAGE LIFE SPAN of man has varied greatly through history and prehistory. The average life span in Greek and Roman times was shorter than that of relative importance of heredity and en­ vironment in governing length of life. There is evidence that exceptional lon­ gevity runs in families, but studies of lower organisms suggest that when the rate of living is taken into account, the total living that individuals can pack into their natural lives is about constant. In other words, if we live longer for genetic reasons we probably do so at a feebler rate, and may not enjoy life so much. Q UESTIONS about longevity might be more easily answered if man were not among the least convenient of organisms for breeding experiments. For some light on the matter we may look to history. As it happens, historians and archaeologists have lately begun to take an interest in population problems and to collect their scattered data. It is not absolutely necessary to start with mortality rates in constructing a human life table. If the assurription can reasonably be made that the total popu­ lation is neither growing nor declining, the distribution of ages among its mem­ bers can be taken as constant in time, and a life table can be computed directly from records of the age at death, as in our fruit-fly study. Such an assumption would be grossly erroneous for popula­ tions in the Western world today, but it may not always have been so. At worst, the historian who is forced to make this assumption in order to use his data is in the same position as the animal ecologist attempting to study mortality outside the laboratory. The life table for the bighorn sheep, for example, was computed in certain prehistoric peoples whose remains have been found in fair numbers. Greatest increase has come in the past 50 years. Maximum life span appears unchanged. this way from skulls picked up on the range and apportioned to age groups by the growth rings on the horns. So it was not altogether improper when the Scottish investigator W. R. Macdonell, following a suggestion of the great English statistician Karl Pearson, studied mortality in ancient Rome and some of its provinces by making use of ages at death obtained from tombstones. Such information is more accurate than might be supposed, for the astrology­ illinded ancients paid attention to pre­ cise birth dates. Other sources of data are court records, especially those hav­ ing to do with inheritance of property; records of burial-insurance societies and other agencies granting annuities, which existed even in Roman times; genealogi­ cal tables; and ages determined on skele­ tons by the surprisingly accurate meth­ ods of physical anthropology. Much more remains to be learned, but a few inferences can be made now without much fear of contradiction. Fseldom or never been so successful as OR one thing, human survival has it is today in the U. S. and western Eu­ rope. No ancient or medieval population boasted a mean longevity greater than about 35 years, whereas the white male born in the U. S. in 1945 can expect to live 65.S years. Primitive man appears to have had a negligible chance' of sur­ viving even to age 60. Longevity appears to be related to culture; however, "civil­ ized" men as such live only a little longer than tribal huntsmen, for urbanization has unfavorable consequences which 60 © 1950 SCIENTIFIC AMERICAN, INC have been circumvented only in modern times. For another thing, there is a stubborn suggestion in some of the data that the well-known enhanced survival of fe­ males over males is a relatively modern phenomenon-primitive societies seem to have worked their women to death at earlier ages. But perhaps the most inter­ esting finding from all these data is that despite the recent dramatic gain in aver­ age life span, there has been no appre­ ciable gain in maximum longevity. Peo­ ple of great age were undoubtedly less numerous in ancient populations than they are now, but there is no reason to think men and women of that time could not live to 115 or 120 if they were lucky enough. There are several authentic­ sounding centenarians among the Ro­ mans studied by Macdonell, including one of 120, and there may even have been some among the 14th-century Brit­ ish group whose vital statistics are pre­ served in the Inquisitiones Post-Mortem. It would be ironic if all the "progress" implicit in modern life tables, and in the medical science that has so changed them, were to come to this: that we have been saved from measles to die of cancer or heart disease. That, however, is the outlook, as well as we can judge it, and the best recipe for longevity would still appear to be the nonoperational one: "choose long-lived parents." • Edward S. Deevey, Jr., is assistant professor of zo­ ology at Yale UniverSity. What GENERAL ELECTRIC People Are Saying W. L. FLEISCHMANN Apparatus Department TURBINE ALLOYS: The application of alloy steels to high-temperature steam-turbine service relies on the accumulation of metallurgical data which are unique in some respects. Where it can usually be assumed that the properties of metals do not change, under the influence of high temperature continuous changes take place. Where ordinarily it is correct to assume that plastic de­ formation will occur only beyond a certain stress, at high temperatures even low loads cause constantly increasing deformation. With a long-life turbine, the data obtained from laboratory tests are then in reality only guides which, by extrapolation, become the bases on which the alloy is formulated and the design stress set. To allow extrapolation, one con­ stantly has to search for indications which may be small in even a year­ long test-but may become im­ portimt in the long life of a turbine. Constant refinements in the test procedures and the theories of the mechanical and thermal behavior of metals under the influence of stress and temperature are, there. fore, necessary to enable us to design the heat-resistant steels. We are confident that this ap­ proach is sound, based upon the year-by-year improvement in ther­ mal efficiency of turbines to 37 per cent, caused in no small measure by the average yearly advance of 12 F in steam temperature maintained for 40 years. These metallurgical developments benefit all of us, since, with the modern efficient turbines, the power industry is able to deliver electricity at low cost to the con­ sumer. Louisi�na Engineering Society, New Orleans, January 13, 1950 * F. B. SCHNEIDER Apparatus Department CYCLONE DUST COLLECTORS: In­ dependent of the design, all "cy­ clones," from the ancient centrifugal dust collectors to the modern vortex collector, suffer from a common handicap, This disadvantage is the large pressure drop caused by the whirling motion of the gas while performing the cleaning action. In addition, with higher dust-separa­ tion efficiency, the pressure drop in­ creases, so that the highly efficient vortex collectors have a pressure drop which is a multiple of the pres­ sure drop of the common centrifugal separators. Since the latter are mostly used in connection with the cleaning of large volumes of air, the power consumed is considerable, and even small reductions of the preSSUl'e will provide substantial savings of horsepower. The pressure drop across cyclone dust collectors can be reduced by relatively simple means. A recovery of 75 percent can be attained on centrifugal separators by employing gradually enlarged tangential inlets together with cylindrical hoods at the outlet. The pressure drop across vortex collectors can be reduced by approximately 80 percent by using diverging inlets and recovery drums at the outlet which discharge clean air into ducts. If the vortex collec­ tors discharge the air into the atmosphere, the pressure drop across them can be decreased by 34 percent with two concentric cones at the outlets, and by amounts up to 80 percent when these cones are com­ bined with a diverging tangential inlet. General Electric Review, Februwy, 1950. * R. O. FEHR General Engineering & Consulting Laboratory SOUND PLEASANTNESS: The pleas­ antness or unpleasantness of a sound determines if an equipment is acceptable from the acoustical standpoint. Sound intensity meters now being used in industry do not give this answer . . . they tell as much about the pleasantness of a noise as a light meter tells about the quality of a painting. Instruments based on new con­ cepts must be built. We believe that 'lfOM. can the ultimate will not be achieved in the near future, but we are well on the way to obtaining practical in­ struments which are far superior to anything we had several years ago. American Society for Metals, Terre Haute, Ind., January 9, 1950 * K. H. KINGDON Knolls Atomic Power Laboratory ATOMIC-ENERGY TRAINING: About 60,000 people are now engaged in the new and potentially large field of atomic-energy work. At present these people are employed directly by the Atomic Energy Commission and its contractors. If the produc­ tion of power from atomic energy becomes an economic reality, such pro.duction will doubtless be partici­ pated in by private industry and will demand additional technical people. Most of the technical people to be used in the atomic-power effort in the future will need training in special fields of current engineering, and in physical, chemical, and metallurgical skills. Perhaps ten percent will need the new fission and neutron knowledge of modern nu­ clear physics. Some of this they will be able to get in universities, but security restrictions and the probably continued general unavailability of nuclear reactors and other expensive and restricted equipment and mate­ rials will mean that much of the specialized technical knowledge will have to be obtained on the job. A considerably larger group than the ten percent mentioned, and con­ sisting of chemists, chemical engi­ neers, and health physicists, will need practical knowledge of how to handle radioactive materials in bulk. Here, again, this knowledge will probably have to be obtained on the job. General Electric Review, February, 1950. put � O� m-­ GENERAL e ELECTRIC 61 © 1950 SCIENTIFIC AMERICAN, INC BOOKS The fighting ship and the airplane as artifacts of modern civilization by James R. Newman JANE'S FIGHTING SHIPS, 1949-50, edited by Francis McMurtrie. JANE'S ALL ' THE . WORLD S AmcRAFT, 1949-50, compiled and edited by Leonard Bridgman. McGraw-Hill Book Com­ pany ($16.50 each). T HIS is the 40th anniversary of the book that was "turned round" in order to distinguish it from an older and more famous companion. The initiate will know at once that I refer to that tall book Jane's All the World's Aircraft and its squat elder brother Jane's Fighting Ships, which last year celebrated its 50th birthday. The issuance of these annuals is always news because of their authori­ tative review of naval and aviation ad­ vances during the preceding year. In a publishing season prospectively as dis­ mal as this one, the Janes' appearance is no less than an occasion. It is the aircraft volume that will receive attention in this review, but I may mention that Fighting Ships is fully up to standard and you will not want to miss it if you are a devotee. All the World's Aircraft is not, one may as well concede, an item for the personal bookcase. It is expensive, some­ what unwieldy and specialized in con­ tent; it will not cut into the market of This I Remember, Decision in Germany, My Three Years in Moscow or The Seven Storey Mountain. Yet in many respects it is a more important and a more inter­ esting book than any of these-more in­ teresting especially if one reads it with sufficient imagination to realize how nu­ merous are its social, economic and po­ litical clues, entirely apart from its wealth of reliable technical data. All the World's Aircraft is an economic geogra­ phy, relating how and where the nations of the world carry on a great manufac­ turing industry; it illuminates the inter­ national situation in providing more for­ midable evidence of the armaments race than can be found in any other single source; it reveals the tension of our pe­ riod, the growing restrictiveness of se­ crecy, as much by its gaps as by the full­ ness of its disclosures; it is an impressive chronicle of scientific and technological progress-largely by way of preparation for world conflict. There is much more of war than of peace in this account of the world's aircraf�-which is a commen- tary on the prevailing political weather and not an indictment of a faithful re­ porter. The work also has its less ominous aspects: the freak craft; the colorful nomenclature; the stories of companies that have become dominant in the indus­ try and of others that from year to year barely manage to survive; the many handsome plates; the occasional side­ light or diverting anecdote; the artists' "impressions" of experimental planes not yet unveiled or, as in the case of Russian aircraft, never to be shown to outsiders unless it be in combat. It is altogether a remarkable achievement of the editorial and book-designing arts-the perfect book, if one's tastes are so inclined, for desultory browsing. The current edition reports on Ameri­ can and British innovations in jet planes; on Russian aviation progress (unfortu­ nately your guesses in this field may be almost as good as Jane's); on the B-36. Although the details are meager, Jane's tells what is known about Bell's 1,000m.p.h. rocket-propelled monoplane X-I and the stainless-steel X-2, designed to obtain even higher speeds. Also de­ scribed are several other experimental planes: Boeing's six-jet light bomber XB-47, which crossed the U. S. last Feb­ ruary at an average speed of 607 m.p.h.; Douglas' extraordinary D-558-2 Sky­ rocket, which resembles a cross between a swordfish and a shark; and the same company's XF3D-l Skynight, a jet­ propelled, carrier-based, all-weather fighter. Fairchild is investigating the use of nuclear energy for aircraft propulsion; Martin has two prototypes of a six-jet experimental bomber; North American is producing a jet fighter, the Sabre, which has exceeded the speed of sound in a dive, and was, according to Jane's, the first American fighter to achieve this feat; the Russians have their four-jet Ilyushin medium bomber, have re-estab­ lished the German Junkers plant in Rus­ sia, and are working intensively on air­ to-air rocket missiles, pilotless aircraft, and the Gurevich, Ilyushin, Lavochkin, Mikoyan, Tupolev, and Yakovlev jet bombers and fighters, many of which have been seen to fly over airfields at "impressively high speeds." I must not forget Northrop's eight-engine jet-pro­ pelled Flying Wing. Judging from ap­ pearances, this is probably the private craft used by Captain Midnight. As an antidote to this report on un­ friendly craft it is agreeable to learn that the Compagnie Fran<;:aise d'Aviation makes an 85-horsepower monoplane named the Cri-Cri, and that Instruments de Precision M.D.G. manufactures a light biplane known as the Midgy Club -the French pronunciation of which is a matter not without interest. Civilians may also take joy in the Fulton alumin­ um Roadable Airphibian, which in three minutes can be turned from a mono­ plane into a convertible coupe; in the Hall plastic-bodied Flying Automobile, almost ready for production; in the Heli­ copters, Inc., five-seat helicopter, which looks exactly like a June bug; in the Hoppi-Copter, early models of which � II WRIGHT BIPLANE was in first edition of All the World's Air-Ships. weighed 90 pounds, could be strapped to the back, flew very well, and con­ tinue in development for their "military possibilities"; in McDonnell's J-l Little Henry, the world's first ram-jet helicop­ ter, which weighs only 280 pounds, hovers nicely with two people, looks rather as if it were made of several large paper clips, and is of serious interest to the Air Force; and in the fact that Piper now has an Aerial Station Wagon, a Vagabond and a Family Cruiser. The fact that this is the 40th anni­ versary of All the World's Aircraft led me to look through a few of the earliest issues of the annual to see what aviation was like four decades ago and to get a view, in fresh perspective, of the rapidity of its evolution. When Fred T. Jane, a most prolific writer, decided in 1909 to put out his "flying annual" All the World's Air-Ships, he had reason to believe that aviation 62 © 1950 SCIENTIFIC AMERICAN, INC j would be on a "practical commercial or even military footing" before very long. Dirigibles, the Zeppelin in particular, were well established; the Wright broth­ ers had made their triumphal tour of Europe, and "concessionaires" were building copies of their famous biplane in Britain, France, Germany, Austria, Spain, Italy and Denmark; B1eriot's Model XI monoplane had flown across the Channel; Voisin, Farman, Handley­ Page and Santos-Dumont were among those engaged in aeronautical research and construction. Jane was handicapped in his "plunge into unknown and unexplored waters" because his editorial labors had to be carried on, as he said, "in a generally unresponsive ocean." Many of the pages of the first annual in 1909 were virtually blank, lacking any photograph and mere­ ly reporting that a certain kind of plane, dimensions and attributes unknown, was under construction in a particular local­ ity. Even so there was much accurate information, and an abundance of the bizarre. In general the planes of 1909 were light, underpowered, unreliable, unpre­ dictable and fairly cheap. Austria, which had "only just commenced to take much interest in aviation," had a few viable types: mono-, bi- and triplanes, including a machine known as the Neme­ thy which weighed 66 pounds and flew -if at all-with a three-quarter horse­ power single-cylinder engine. Belgian engineers had hatched the De La Hault and the Vandenbergh "Flappers"-craft whose wings gave "bird action" if not bird results-but more plausible engines were also being developed in Belgium. Of China Jane remarks that while no flying machines were yet to be found there, it should not be forgotten that these people "with their thousands of years of kite flying, are likely to be apt pupils in all that pertains to the science of wind resistances, etc." In England flying attracted "neither interest nor attention," apart from bal­ loon ascensions, until 1908. Then sud­ denly new machines began to appear and popular concern with aviation be­ came widespread. Jane records that in 1909 there were six "aerial societies," five "aerial journals," and no fewer than seven "flying grounds." But he laments the "extreme tendency of the British in­ ventor to isolate himself and work in secret," which is responsible for the fact that so many of the pages in his British section are bare of detail. British manu­ facturers in 1909 were building the An­ toinette monoplane, a very respectable­ looking affair with warping wings and a 100-horsepower engine; the B1eriot monoplane; the Handley-Page, whose design required that it leave its wheels behind when it took off and land on fixed runners; the Cody military biplane, later models of which were used in the early - part of the First World War; a Windham monoplane with nonrigid wings and large bamboo booms, exactly resembling the flyers that children make out of single sheets of paper; and, among many oth­ ers, a Saul I that weighed 160 pounds, had an eight-horsepower motor, was made of hickory wood, and could not possibly have flown unless borne aloft by a tornado. In those days France held the first position in aviation. It had 13 societies, 14 journals, 13 fields with hangars, An­ toinette planes, BJeriot biplanes and monoplanes, 39 Voisins, 59 Wrights and Santos-Dumont's several models of La Demoiselle, a very successful craft though it was the "smallest man-carrying aeroplane in existence." France also had its own curiosities: the Marquis d'Eque­ villey's oval craft, resembling the cross section of a pumpkin; Levy-Caillat's monoplane, an obviously earth-bound sled on wheels; a Witzig-Liore-Dutilleul which looked like a flight of stairs and probably performed as well in the air; several helicopters, one of which, the Bartin, was quite modern in appearance; and finally Givaudan's inert affair-two concentric drums joined by a triangular girder, which, it was said, could not heel over when turning and was "unaffected by side gusts of wind" and, no doubt, by any other efforts to get it aloft. Germany was industrious as always, but her main success up to 1909 had been with the Zeppelins. By 1913, how­ ever, Jane found in Germany well over 80 "aerial societies," Army flying schools, 200 "war-effective planes" and 200 more building. All in the latter group were equipped with "bomb droppers" and photographic apparatus. Another ambi­ tious people, the Japanese, had a similar record. In 1909 Japanese aviation con­ sisted of a single Yamada biplane (a copy of a Wright) and a biplane "de­ signed by the American steel capitalist John W. Harrison," which was described as a "street car with the sides knocked out and replaced by slender rods." Four years later Japan had a military and a naval air arm, numerous flying grounds, half a dozen new models and at least two dirigibles-copies, to be sure, of German and American types. Of Russian craft, Jane's had not a picture to show in 1909, though at least nine types, including Farmans, Voisins and Wrights, were said to be building. Five years later general attention to military aviation in Russia was "only second to France." By then even Mexico, Peru, Norway, Serbia, Portugal and Rumania had military air forces. The first issue of Jane's appears to have approached the subject of aviation in the U. S. with an air of condescension and occasional incredulity, not to men­ tion a considerable body of misinforma­ tion. Jane noted that no fewer than 8,000 persons in the U. S. were reported to have flying-machine deSigns "in some stage or other," but he skeptically cut CHECK THE O NES YOU WANT AND SEE THEM ON APPROVAL �� � 1. Tec nical Sketchmg AND ' , VISUALIZATION FOR ENGINEERS By Katz Teaches in clear, simple steps how to plan and execute accurate freehand technical sketches of all kinds-an invaluable aid in put­ ting across your ideas and transmitting engineer109 information clearly and qUickly. Here is a skill that will help you immeasurably in (he design conference, shop, sales office and on innu­ merable other occasions. $5.00 2. Working with People By Uris & Shapin Can you use a bigger salary? 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" V' 31 , r __________... ____ ... 63 © 1950 SCIENTIFIC AMERICAN, INC I I I I I I I I From the editorial rooms of The Beacon Press, Boslon Ethics of Relativity Outlined in New Book RELATIVITY -A RICHE R TRUTH. By Philipp Frank. Fore· word by Albert Einstein. 160 pages. Boston: The Beacon Press. At all bookstores, 2. Here is the answer to all those who thought that relativity would undermine morality or truth. Einstein's succes­ sor to the Chair of Physics at the Uni­ versity of Prague, the leading author­ ity on Einstein's life and \vorks, explains simply and accurate­ ly the ethical im­ plications of reIa­ Einstein's own "cosmic tlVlty and religion." Professor Frank's style is outstanding for its clarity and simple charm. Be is writing about things that matter to all of us-the difference between true and false and between right and wrong. Precisely because he is an outstanding scientist, he is impatient with long words that hide the truth. Says Charles N. Morris, author of Signs, Language and Behavior: "The current opposition between man as knower and man as valuer is destroyed at its roots in Relativity-;A Richer Truth. This is a little book, but a big one." feed hungry minds • • • Doctors overseas are hungry for facts on recent medical . research_ must The farmers' skill be nourished techniques to on increase new food crops. Teachers, scientists, en­ gineers need the books that are the tools of their trade. Make a lasting contribution to recovery! sends As new little books, as in $10 your name, to war-wrecked schools and libraries in Europe or Asia. Mail your cash donation in any amount, or requests for full inf Tmation, toBOOK PROGRAM (�1' Ill� 20 Broad St., New York 5, N. Y. Or Your Local CARE Outlet this figure to 800. One is interested to read in the 1909 Jane's of such flying fields as Hemstead [sic] and Westburg [sic] on Long Island. Among the more interesting planes were Curtis' improved June Bug biplane, Eichenfeldt's extraor­ dinary-looking biplane priced at $1,000 ("very successful and remarkably sta­ ble"), and the Wright brothers' beautiful machine, of which 82 had already been ordered. In the odd category I should mention V. L. Ochoa's Jersey Mosquito ("shown at Arlington, May, 1909, but did not fly"); Kimball's biplane, which was christened by the "famous American actress Vera Held" but failed to live up to this accolade because its five "propel­ lers would not all work"; Rickmann's combination bicycle and umbrella, which neither flew, rode nor protected one from the rain; Thompson's Air Suck­ er; Roshon's Multiplane with 13 wings, and Irvine's flying Ferris wheel. From these beginnings came the air­ craft of today; and studying Jane's in 1950 one wonders whether some of the odilest specimens at the bottom of the tree did not contribute almost as much to the process of evolution as did their more respectable and rational relatives. One point is quite clear: the emphasis on military aviation is a characteristic disease of the century and not merely of its mid-point. In 1909 Jane's spoke with optimism of the peacetime potentialities of aviation. But even in this first issue there was an article on aerial warfare by Admiral Sir Percy Scott and another on the political aspects of aviation, mostly military, by L. Cecil Jane. (This Mr. Jane aired a number of interesting opinions, among them the thought that while "international war, commerce and locomotion will be in some degree af­ fected by aviation . . . it may be sug­ gested that the forcible carrying through of the'social revolution' is no longer pos­ sible" because aircraft denies the "masses of the people" the "supremacy" needed to bring about abrupt political change. "Even one solitary airship would 'be sufficient to disperse a crowd; a fact which makes [dangerous and subver­ sive] fraternisation even less probable.") The fifth issue in 1913 left no doubt of the military trend. Its preface ob­ served that five years earlier the aero­ plane had been regarded only as a ma­ chine which was "going to oust the motor car as a sporting vehicle. . . . Beyond that, nothing!" The 1913 preface went on: "Today everything is completely changed. . . and it is as a war machine that the aeroplane has come into its o\vn." T HE HISTORY AND SOCIAL IKFLUENCE by Redcliffe N. Salaman. Cambridge University Press ($10.00). Dr. Salaman spent over 40 years studying this "inoffensive vege­ table," and a great social and economic OF THE POTATO, Special Pre-Publication Offer TO SCIENTIFIC AMERICAN READERS on two important additions to The Life of Science Library. Regular list price $4.00 each. All orders received on or before May 10th will be filled at the spe­ cial pre-publication price of $3.50 each. Harvey Cushing SURGEON, AUTHOR, ARTIST By ELIZABETH H. THOMSON An authoritative, highly readable biography of an olympian figure of the twentieth century. His tre­ mendous achievements in brain surgery, his Pulitzer-prize-winning biography of Sir William Osler made Harvey Cushing a world famous figure. But tbis book pre­ sents Cushing as a husband and father as well-and what emerges is a full length portrait of a great man. (Vol. 13) Publication: May 11 $4.00 Man the Maker A History of Technology and Engineering By R. J. FORBES • The fasci­ nating story of man as a tool-using animal from Paleolithic times to the present. (Vol. 14) Lewis Mumford: "An excellent, compact history of technics." Publication: Late May $4.00 The first 12 volumes in The Life of Science Library are now ready. See these and many more to come in one of the most exciting publishing ventures in science literature. For full information about these books and how to buy them most eco­ nomically check the box indicated on the coupon below. r USE THIS COUPON TO SEND US YOUR ORDER TODAY'l To Henry Schuman, Inc. I I I I I I I I I I L 20 East 70th St., New York 21, N. Y. I enclose check or money order. 0 HARVEY CUSHING $3.50 (after May 10. $4.00) 0 MAl(al::EM�:���l��O 0 At no obligation send me information on Life of Science Library. I I I I I I I I I Name... Address.. City........................ Zone....5tate ....................... .JI ----------------- 64 © 1950 SCIENTIFIC AMERICAN, INC 1 JUST PUBLISHED Measu mg Our universe From the Inner Atom to Outer Space By OLIVER. JUSTIN LEE, Director Emeritus, Dearborn Observatory. How do scientists measure one-trillionth of an inch-a bil­ lion light years-the inner vastness of the atom-the outer vastness of cosmic space? A distinguished astronomer tells you in this new book what scientists know about distances, and how they know it ... what methods they use and the importance of accuracy in measurement. This is the story of man's long struggle with the problem $3.00 of measuring distances. Illustrated. PHYSICS TEllS WHY An Explanation of Some Common Physical Phenomena by OVERTON LUHR. Here is a valuable understanding of how the basic laws of physics apply [0 the natural phenomena and to new developments Hnd today's inventions. "One of the most charming, most popular, and most highly praised volumes in its own or any field." American Scientist. Illustrated with lively cartoons. $3.75 Sa"'i-EKPlIJRINfi ElECTRICITY Ma1z's Unfinished Quest by HUGH HILDRETH SKILLING. A readable presentation of the continued story of electricity from ancient to' the presenc. Reveals liuie known and in m te facts about the scientists-great and small -who contributed to the advancement of electrical science. " .. . should be coHateral reading for all those whose studies take them into this field." The Scientific Monthly Illustrated. $3.50 times ti a SltYSNlJ1J TINI Hunting the Stars with Your Camera by R. NEWTON MAYALL and MARGARET L. MAYALL. This exciting book tells what there is in the heavens to photograph and how to "shoot" it. It contains simple and understandable data on photographic details, as well as ample material on astronomy, telescopes. and other equipment. The book proves, by excellent photographs, that the amateur can produce astronomical pictures of . beauty and scientific value. Illustrated. $3.75 THE RONALD PRESS COMPANY 15 E. 26th St . I I • I • New York 10, N. Y. the books checked. Within 5 days I will either remi t full price , plus mai li ng charge, or return the books (We pay delivery if you remit with order.) Measuring Our Universe, Lee .. .... . . .. $3.00 Physics Tells Why, Luhr .. . . .. . .. ... .. . .. . . .. 3.75 Explorinl1 Electricity, Skilling ..... .. .. .... .. 3.50 Sky.hootmg, Mayall.Mayall ..... .. ... . . . . ...... 3.75 SEND ME ' � I I I Name................. ........................... .. I ��;��.�.�.:::::::.:::: :::::::::::·i���:::·s;�;� ::::::::::: I 203-. - - - - �- - - - - - _. M history is the crown of his labors. It be­ gins with the cultivation of the potato in South America, perhaps 2,000 years before Columbus, traces the story to modern times, and examines the potato's effects upon the social structure of those peoples-principally in the United King­ dom-who "adopted it as a staple article of diet or an essential product of their economy." In Salaman's account of its earlier history, of the potato's many names and aliases, of the differing opinions as to its "'vertues,' vices and values," of the Raleigh legend and other legends about its origin, of the varieties of potatoes, "past, present and future," of its crucial role in Irish history ("after proving itself the most perfect instru­ ment for the maintenance of poverty and degradation amongst the native masses, the potato ended in wrecking both ex­ ploited and exploiter"), of its relation to labor problems and politics, of its ap­ pearance in literature and art-in short, in the many pages of his monumental treatise there is scarcely a dull passage. T HE MATHEMATICS OF GREAT AMA­ TEURS, by Julian LowellCoolidge. Ox­ ford University Press ($6.00). Sketches of the original mathematical cont:ribu­ tions of 16 "amateurs," that is, men most of whom are known principally for their activities in other fields. The group in­ cludes Plato (numbers, commensura­ bility, mean proportion), Omar Khay­ yam (cubic equations), Leonardo da Vinci (areas of lunes, inscription of regular polygons, etc.), Albrecht Durer (descriptive geometry), Blaise Pascal (arithmetic triangle, Pascal's theorem, etc.), John Napier, Baron of Merchis­ ton (logarithms), Viscount Brouncker (continued fractions, etc.), Guillaume L'Hopital (infinitesimal analYSiS, conic sections, etc.), Comte de Buffon ("moral arithmetic" and geometric probability), Denis Diderot (vibrating strings, in­ volutes), William George Horner (his "method"), Bernhard Bolzano (function theory, paradoxes of the infinite). While the choices, as the author concedes, are a triBe inconsistent (Fermat, for exam­ ple, is omitted because he was the "Prince of Amateurs"; Napier and Horner are included though clearly not "known for their activities in other fields"), this is an uncommonly interest­ ing work-scholarly, readable, well illus­ trated. N J. P. Lockhart-Mummery. Andrew OTHING NEW UNDER THE SUN, by Melrose Ltd., London (12 shillings six­ pence). A collection of popular essays, mostly on out-of-the-way subjects in natural history, loosely brought together under the theme which has been ex­ pressed in many ways, and which in Robert Herrick's line goes: "Nothing is new; we walk where others went." Dr. Lockhart-Mummery, a surgeon, writes easily and well and his little book is as � Here's a selection ?f your favorite after·hours reading ... new Science Fiction hit books by four top writers. MAX Ehrlich THE BIG EYE For six months a Science Fiction bestseller and now the selection of a major book club. The story of an astronomical discovery, through the "big eye" at Palo· mar that brought peace to the wor d at a dreadful price. S2.50 i ROBERT A. Heinlein WALDO and MAGIC, INC. The story of Waldo, interplane· tary "fixer" (when he felt like it and was paid enough). and the m a r v e l o u s f a n t a s y abo u t racketeering i n the magic busi .. n e s!-two r e c o g n i z e d classics complete in one volume for your S2.50 permanent library. Asimov PEBBLE IN THE SKY A highly ingenious tale of Ga­ lactic Era 827. in which a re­ tired tailor from forgotten old Chicago prevents a galactic war and promotes a romance. 52.50 Clement HAL NEEDLE Symbiosis-and a symbiote-feature this provoca­ tive and exciting novel about a cosmic chase which has its smash finish on Earth! Just out, 52.50 � COMING in May - THE MARTIAN CHRONICLES by Ray Bradbury, prize-winning Story writer who has staked out the red planet as his special province. Reserve your copy of this Science Fiction publishing event now . 65 © 1950 SCIENTIFIC AMERICAN, INC pleasant an hour or so of reading as you are likely to run across in this field. M by Sir Thomas Heath. Oxford University Press ($5. 50). In this posthumous work Sir Thomas Heath, a noted historian of Greek mathematics, presents a fresh translation of Aristotle's mathematical writings and an appraisal of his contri­ bution to the subject. Aristotle was clearly not a professional mathematician and shows in his works no acquaintance with the higher branches-conic sec­ tions for example. Yet he was fully abreast of the elementary mathematics of his time, was much given to mathe­ matical illustrations-the incommensur­ ability of the diagonal of a square was one of his favorite didactic devices-and threw a "flood of light," as Sir Thomas points out, on the accepted principles and methods in use immediately bcefore Euclid. A careful and, as is always the case with Heath's writings, readable study, of particular value to philoso­ phers, mathematicians and historians of science. This treasury of good reading is not for sale at any price. But it's yours FREE with a trial subscription to the N AVALCADE is a handy, pocket size an­ thology of the most memorable articles which have appeared in The Saturday Review in the past quarter century. The:' ".-� articles of sueh enduring value that newsp ..._