PHYSICS. 379 



In the preparation of the uranyl chloride a form of this salt was 

 obtained consisting of well-crystallized, non-hygroscopic, tri-clinic 

 plates. These when excited at the temperature of the room exhibited 

 a brilliant fluorescence spectrum of striking symmetry, which instead of 

 the usual group of seven or eight bands was resolved into eight groups, 

 each consisting of five very narrow, nearly equidistant bands, the 

 arrangement of which repeats itself with exactness in each group. 

 This remarkable spectrum has been studied in detail at various temper- 

 atures between +20° and —185° C. and the results will be described 

 at length in a forthcoming number of the Physical Review. 



The preliminary study of the fluorescence of frozen solutions of the 

 uranyl salts, referred to in Year Book No. 12, has been completed, and 

 the results have been published in the Physical Review (second series, 

 vol. Ill, p. 457). The detailed investigation of the complicated effects 

 observed when fluorescence is excited under varying conditions as to 

 dilution and temperature has since been completed by Mr. H. L. 

 Howes and his determinations are now being prepared for publication. 



The investigation of the decay of phosphorescence at low tempera- 

 tures by Dr. E, H. Kennard has been completed and is published 

 (Physical Review, second series, vol. iv, p. 278). He finds the linear 

 relation between time and the reciprocal of the square root of the 

 intensity to hold for cetyl alcohol and kerosene, but that in the case of 

 paraffine the decay during the later stages increases in rapidity with 

 time and that the intensity of phosphorescence is expressed, within 

 the errors of observation, by the equation 



During the year covered by this report quantitative studies have 

 been completed on the luminescence of kunzite (Nichols and Howes^ 

 Physical Review, second series, vol. iv, p. 18). 



The red and blue bands in the fluorescence spectrum, at 0.590// and 

 0.432/i, previously described by Pochettino, were located and mapped, 

 together with the associated bands of absorption. The relative bright- 

 ness of the two bands in the case of pink and of w^hite kunzite was 

 determined and the effect of temperature on the form and location of 

 the red band was noted. The study of the phosphorescence of the red 

 band after kathodo-bombardment brought out a law of decay not 

 hitherto definitely established for any phosphorescent substance. An 

 initial (so-called ''linear") process of very short duration was found to 

 precede the two such processes commonly observed. 



Dr. Frances G. Wick, an account of whose investigation of the 

 fluorescence, absorption, and surface color of the platino-cyanides has 

 been published in the Physical Review (second series, vol. iii, p. 382), 

 made observations during the summer of 1914 on the fluorescence 



