PHYSICS. 315 



Nichols, E. L., Cornell University, Ithaca, New York. Grant No. 840, 

 allotted December 13, 1912. Systematic study of the properties of 

 matter through a wide range of temperatures. (For previous reports 

 see Year Books Nos. 4-11.) $3,000 



(1) Fluorescence and phosphorescence: 



The year's work on the spectra of the uranyl salts has been chiefly 

 devoted to the detailed study of the very comphcated groups of 

 series of narrow bands existing in the fluorescence and absorption 

 spectra of these salts at the temperature of liquid air. In addition 

 to the series described by Becquerel and Onnes, we find numerous 

 other series of nearly if not exactly constant frequency differences and 

 having nearly the same intervals for the various salts. Many photo- 

 graphs of these spectra have been measured and charted and the 

 results are now being discussed and compared to determine in how 

 far the various salts have series in common and to establish if possible 

 the effect of molecular weight and of the presence of water of crystal- 

 lization upon the location and character of the bands. Besides this 

 study of the spectra of these salts in the solid form a preliminary in- 

 vestigation has been made of the fluorescence spectra of their aqueous 

 and alcoholic solutions, frozen and excited at various temperatures 

 down to 180° C. An account of the many striking and significant 

 modifications which these spectra undergo when the concentration 

 and the temperature of excitation are varied will be pubhshed in a 

 note now in preparation. Mr. H. L. Howes, who has assisted us 

 throughout the experiments above described, has in hand a detailed 

 investigation of the spectra of these solutions. 



Dr. G. E. Thompson has completed the study, in which he has been 

 engaged for the past three years, of the electro-motive forces devel- 

 oped in certain cells with electrolytes consisting of alcoholic solutions 

 of rhodamin and other fluorescent substances when exposed to light. 

 He finds that while the effect is selective, as regards the wave-length 

 of the effective rays, the exciting band apparently coincides with 

 neither the fluorescence band nor the absorption band of the solution, 

 but has its maximum further towards the violet. While all wave- 

 lengths capable of producing electromotive force also excite fluo- 

 rescence, and while the effect has been observed only with fluorescing 

 solutions, there does not appear to be any very intimate connection 

 between the two phenomena. 



Dr. E. H. Kennard has been engaged in an investigation of the law 

 of the decay of phosphorescence of certain organic substances when 

 excited at the temperature of liquid air. It was thought that the 

 curves of decay hitherto studied might owe their complex character 

 to the lack of homogeneity and that substances which are physically 

 homogeneous might show a simpler form. This has been found to be 

 true with the materials thus far examined, i. e., kerosene oil and par- 



