Duane and his collaborators repeated the Compton experiments at Harvard, using again the ionization chamber method, and failed to obtain any trace of the Compton shift. At the February meeting of the Physical Society, 1924, they took the view that the Compton effect did not exist, but that what both Compton and Ross had observed was the -rays of molybdenum with their energy diminished by the work necessary to eject electrons from the shell of the carbon atom.[192] This would actually produce a “scattered line” from carbon which would be practically coincident with Ross’s published line, though it should not give a dependence of upon angle such as Compton had observed. A few weeks before the date of this writing, at the Norman Bridge Laboratory of Physics at Pasadena, Becker, Watson, and Smythe,[193] using aluminum as a scatterer, obtained a Compton-effect photograph which showed both components of the -rays of molybdenum displaced by an amount which could be measured with an accuracy of about 1 per cent (as checked by the author) and within this limit the agreement with the displacement computed by the foregoing Compton equation was exact. In this case the Duane-effect-line is completely removed from the Compton-effect-position, and it too was found upon the photographic plate. This furnishes, I think, unambiguous evidence for the reality of the Compton effect. Ross also informs me that he has obtained the Compton shifted line from a number of other elements besides carbon—elements in which the Duane effect could not possibly be confused with it. [Pg 260] The accompanying plate sinews in Fig. 36 one of the Becker, Watson, and Smythe recent photographs. This one was not taken with sufficient resolution to show the -line as a doublet, but is more reproducible than the one that did. The direct images of both the - and -lines of molybdenum are shown, labeled and , and, a short distance to the right of each, appears the displaced Compton-shifted-line marked and . At the moment, then, Einstein’s hypothesis of localized light-quanta is having new and remarkable successes. Duane,[194] Epstein,[195] and Ehrenfest[196] have perhaps made some slight advances also in the direction of accounting for interference in terms of it. But the theory is as yet woefully incomplete and hazy. About all that we can say now is that we seem to be driven by newly discovered relations in the field of radiation to the hypothetical use of a fascinating conception which we cannot as yet reconcile at all with well-established wave-phenomena.