792 THE BELL SYSTEM TECHNICAL JOURNAL, OCTOBER 1951 



experiments were continued it was found that the distribution-in-angle of 

 the scattered electrons had been completely changed. . . . This marked 

 alteration in the scattering-pattern was traced to a re-crystallization of the 

 target that occurred during the prolonged heating. Before the accident and 

 in previous experiments we had been bombarding many small crystals, but 

 in the tests subsequent to the accident we were bombarding only a few 

 large ones. The actual number was of the order of ten." 



I do not know whether Davisson ever cried out felix culpa! in the lan- 

 guage of the liturgy; but well he might have. The exploding liquid-air 

 bottle blew open the gate to the discovery of electron-waves. Fatal conse- 

 quences were not wanting: the accident killed the flourishing study of 

 polycrystalline scattering-patterns, and countless interesting curves for 

 many metals are still awaiting their discoverers. This may illustrate a differ- 

 ence between the industrial and the academic career. Had Davisson been a 

 professor with a horde of graduate students besieging him for thesis sub- 

 jects, the files of Physical Review might exhibit dozens of papers on the 

 scattering-patterns of as many different metals, obtained by the students 

 while the master was forging ahead in new fields. 



Now that we are on the verge of the achievement which invested Davis- 

 son with universal fame and its correlate the Nobel Prize, I can tell its 

 history in words which I wrote down while at my request he related the 

 story. This happened on the twenty-fifth of January, 1937: 1 have the sheet 

 of paper which he signed after reading it over, as also did our colleague 

 L. A. MacCoU who was present to hear the tale. This is authentic history 

 such as all too often we lack for other discoveries of comparable moment. 

 Listen now to Davisson himself relating, even though in the third person, 

 the story of the achievement. 



''The attention of C. J. Davisson was drawn to W. Elsasser's note of 

 1925, which he did not think much of because he did not believe that 

 Elsasser's theory of his (Davisson's) prior results was valid. This note had 

 no influence on the course of the experiments. What really started the dis- 

 covery was the well-known accident with the polycrystalline mass, which 

 suggested that single crystals would exhibit interesting effects. When the 

 decision was made to experiment with the single crystal, it was anticipated 

 that 'transparent directions' of the lattice would be discovered. In 1926 

 Davisson had the good fortune to visit England and attend the meeting of 

 the British Association for the Advancement of Science at Oxford. He took 

 with him some curves relating to the single crystal, and they were surpris- 

 ingly feeble (surprising how rarely beams had been detected!). He showed 

 them to Born, to Hartree and probably to Blackett; Born called in another 

 Continental physicist (possibly Franck) to view them, and there was much 



