Professor Dempster and the American Association PrizeSource: The Scientific Monthly, Vol. 30, No. 4 (Apr., 1930), pp. 375-376Published by: American Association for the Advancement of ScienceStable URL: http://www.jstor.org/stable/14618 .

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THE PROGRESS OF SCIENCE PROFESSOR DEMPSTER AND THE AMERICAN ASSOCIATION PRIZE

THE1E seventh awiard of the American Association prize of $1,000 was made at Des Moines to Dr. A. J. Dempster, professor of physics in the University of Chicago. This prize is awarded an- nually to the author of a notable contri- bution to the advancement of science presented at the annual meeting. The funds for the prize are generously sup- plied by a member who does not wish his name made public. The committee on award was this year composed of the fol- lowing members: Charles E. Allen, Uni- versity of Wisconsin, chairmian; P. W. Bridgman, Harvard University; Fay- Cooper Cole, University of Chicago; S. C. Lind, University of Minnesota; H. L. Ri'etz, University of Iowa.

Dr. Dempster 's contribution consti-

tutes an importaint extension of the work of the Frenchi physicist, Louis de Broglie, for which the Nobel prize in physics was recently awarded. Dr. Arthur H. Compton has said that "the most important contribution of twen- tieth century physies is that the physi- cal world can be reduced to three kinds of particles, protons, electrons and pho- tons, and that each of these particles has also the characteristics of waves. The last stage of this work is the proof that protons, the positively charged parts of matter, have wave character- istics. It is this completion of the great work of twentieth century physics which has been accomplished by Professor Dempster. "

According to Professor Henry G.

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376 THE SCIENTIFIC MIONTHLY

Gale, president of the American Physical Society, "physicists, seeking to explain the ultimate inature of things, had be- lieved that light was simply a wave form, and that atonms, which consist of negative electrons revolving around a positive nucleus, or proton, were simply particles. Professor Corupton in 1926 proved that light is not only a wave but also a stream of particles, or photons, bunldles of radiant energy. In 1927 two investigators at the Bell Laboratories, Davissoni and Germer, revealed that the negative electrons are niot only particles but that each particle also acts as a wave. The final evidence in the cycle has now been adduced by Dr. Dempster, who has proved that the positive protons have also wave-form as well as particle- form. These three discoveries are prob- ably the most striking advances in phys- ics in recent years."

Professor Dempster, during the last eight months of experinmentation, suc- ceeded in taking photographs of the positively charged hydrogen nuclei in a manner which proved them to be vi- brating, approxinmately 1,000,000 times as fast as ordinarv light. By shooting the protons tlhrough a crystal in a vacuum, he wIas able to show pattern marks oin the sensitized plate. If the proton had been merely a particle with- out vibrationl, nothing but a dot wouldl have been revealed oni the photographic plate.

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plained by Professor Dempster as being similar to the diffused appearance of sunlight through an umbrella, a phe- nomenon peeuliar to things having a wave-form. " In these experiments a calcite crystal takes the place of the umbrella, and is used as a mesh to con- trol the particles. The hydrogen pro- tons in these experiments penetrated the crystal in much the same way that light photons would, and their patterns on the photographic plate leave no doubt as to their wave-properties. The experiments completed have so far been confined to hydrogen. But since all the elements consist of the sanme thing or things, in different arrangement, it can be as- sumed that the protons of all substances would act in the same manner. Hydro- gen is the simplest of the elements. We are now applyillg the method to helium, the next silmplest. Ilow protons, elec- trons and photons can be both waves and particles at the samne time is per- haps the greatest problemu now confront- ing physicists. This experiment does not throw direct light upon that obscure relationship but helps to clarify the problem."

Dr. Dernpster, wh o is forty-three years old, has beeii a mnember of the physics departmn-ent of the University of Chicago for fifteen years. He is a grad- uate of the University of Toronto and of the University of Chicago, and has studied at G-6ttingen, Mutnich and W-urzburg.

THE TOTAL ECLIPSE OF THE SUN IN CALIFORNIA

THE first total eclipse of 'the sun for 1930 will occur on April 28 across a nar- row strip' of California about half a mile wide. In answer to a request by the University of California that the army air service cooperate with Lick Observa- tory in observations of this eclipse, President W. W. Campbell has received

word from the U. S. army headLquarters in San Francisco that the requisite type of plane is available and that such co- operation will be gladly offered.

Tentative plans call for the services of one plane at an altitulde of not less than 10,000 feet, over Napa Valley, between Napa and St. Helena, and perhaps of

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