THE SCIENTIFIC WORK OF C. J. DAVISSON 787 



work was presented before the April meeting of the American Physical 

 Society in 1911. Abstracts of the papers which he there gave orally may be 

 found in Physical Review, but the publications in full appeared (in 1912) in 

 Philosophical Magazine. Davisson's choice of a British journal was advised 

 by his transplanted teacher, but it must be realized that in 1912 the Physical 

 Review had by no means ascended to the rank that it holds today. With 

 this work came to their end the contributions of his student years, and next 

 we find him publishing as an independent investigator. 



From Davisson's years (1912-17) at the Carnegie Institute of Tech- 

 nology there is a paper embodying an attempt to calculate the optical dis- 

 persion of molecular hydrogen and of helium from Bohr's earliest atom- 

 model. It shows him possessed of no mean mathematical technique, but is 

 based — as the date by itself would make evident — on too primitive a form 

 of quantum-theory. 



In June 1917, in the midst of World War I, Davisson came for what he 

 thought would be a temporary job at the institution then known as the 

 Research Laboratories of the American Telephone and Telegraph Company 

 and the Western Electric Company, thereafter — from 1925 — as Bell Tele- 

 phone Laboratories. Not for a year and a half was he able to devote him- 

 self to work untrammeled by the exigencies of war. So far as publication is 

 concerned, his second period began in 1920, when he presented two papers 

 before the American Physical Society: one at the New York meeting in 

 February, one at the \\'ashington meeting in April. In the former of these 

 his name is linked with that of L. H. Germer, a name associated with his 

 in the great discovery of electron waves; in the latter it is linked with that 

 of the late H. A. Pidgeon. 



These two papers are represented only by brief abstracts; and this is the 

 more regrettable, as they form the only contributions published under 

 Davisson's name to the dawning science of the oxide-coated cathode. In 

 the former, he estabHshed that the remarkably high electron-emission of 

 oxide-coated metals — as contrasted with bare metals — is not due, as had 

 been elsew^here suggested, to the impacts of positive ions from the gas of 

 the tube against the coatings: it is true thermionic emission. In the latter, 

 he studied the rise and eventual fall of the thermionic emission as more 

 and more oxide is laid down upon the metal surface, and concluded that 

 the emission occurs when a definite number of oxide molecules is assembled 

 into a patch of definite size on the surface: the number of patches of just 

 the right size first rises, then declines as the deposition continues. According 

 to colleagues of his, these two papers fall short by far of indicating the ex- 

 tent of his contributions to this field; and one of them has said that Davis- 

 son was excessively scrupulous about putting his work into print, being 



