PHYSICS. 381 



Lewis, E. P., University of California, Berkeley, California. Photographic 

 investigations of vacuum-tube spectra of gases and vapors. (For previous 

 reports see Year Books Nos. 3 and 14.) 



During the past year Professor Lewis has completed and published 

 a paper on the Ultra- Violet Spectrum of Krypton, which was printed 

 in the Astrophysical Journal for January 1916, pages 67-72. The wave- 

 lengths of about 150 lines previously unobserved were measured and 

 some series relations were discussed. Work begun on absorption spectra 

 in the ultra-violet, which was discontinued for a time on account of 

 pressure of work, will shortly be resumed. 



Nichols, E. L., Cornell University, Ithaca, New York. Systematic study of 

 the properties of matter through a wide range of temperatures. (For 

 previous reports see Year Books Nos. 4-14.) 



The general survey of the spectra of the uranyl salts, both as regards 

 fluorescence and absorption, a work of four years, has been completed. 

 The photographs have been measured and the results computed, tabu- 

 lated, and mapped by Dr. H. L. Howes. The materials thus worked 

 up include the various salts made for us by Mr. Cragwall and numer- 

 ous additional preparations by Dr. Wilber. In addition to this general 

 survey, the data from which will appear in tabular and graphic form 

 in a monograph on the uranyl salts now in preparation, various more 

 detailed studies have been made or are in progress. 



The Nitrates. 



A critical examination of the fluorescence and absorption spectra 

 of several forms of crystallized uranyl nitrate has been completed,^ 

 the special object being the determination of the influence of different 

 amounts of water of crystaUization. The nitrate is well suited for 

 such a study, because at least three different hydrates are known 

 besides the anhydrous salt. It is found that the spectra of the three 

 hydrates differ from each other and from the spectrum of the anhy- 

 drous nitrate fully as much as do the spectra of as many different 

 uranyl salts. It appears, therefore, that water of crystallization 

 exerts as great an influence upon the vibrating electrons of the 

 UO2 base as is exerted by the acid component of the salt. The 

 interval between bands was found to increase slightly with increasing 

 amount of water of crystallization. It was also found that each of 

 the numerous series of absorption bands has its origin in the reversing 

 region, the first member of the absorption series being in coincidence 

 with the final member of a fluorescence series. While in many cases 

 either the fluorescence band or the absorption band in the reversing 

 region was absent, so that the actual reversal could not be observed, 

 the positions computed from the frequency intervals of the two series 

 almost always indicate that the above-mentioned relation exists. This 

 is presumably true of all uranyl spectra. 



'Nichols and Merritt, Physical Review (forthcoming). 



