254 REPORTS ON INVESTIGATIONS AND PROJECTS. 



Nichols, Edward L^ Cornell University, Ithaca, New York. Grant 

 No. 286. Qjiajititativc study of fluorescence and phosphorescence, 

 especially at loiv temperatures. $1,000. 



Report. — While the investigation, carried on in cooperation with 

 Prof. Ernest Merritt, is intended to include the general subject of 

 luminescence, the experimental work completed during the current 

 year has had to do with the luminescence of sidot blende, a phos- 

 phorescent zinc sulphide that seems especially well suited to bring 

 out the relationships existing between different types of lumin- 

 escence. This substance is rendered luminescent by all known 

 exciting agents, such as light, the Roentgen rays, radium rays, and 

 cathode rays. Quantitative measurements of the luminescence ex- 

 cited by Roentgen rays have been made and the photoluminescence 

 of sidot blende during excitation and subsequently has been deter- 

 mined. The results of these measurements are described in a paper 

 in the October number of the Physical Review. This paper is the 

 fifth of the series of studies of luminescence, for the further prosecu- 

 tion of which this grant has been made, and it is proposed to incor- 

 porate the substance of these and of the subsequent papers of the 

 series in a final report to the Carnegie Institution of Washington. 



The papers of this series already published bear the following 

 titles : 



1. The phosphorescence and fluorescences of organic substances at low tempera- 



peratures, Physical Review, vol. 18, p. 355. 



2. A spectro-photometric study of fluorescent solutions belonging to Lommel's 



first class, Physical Review, vol. iS, p. 403. 



3. On fluorescence spectra. Physical Review, vol. 19, p. 18. 



4. The influence of light upon the absorption and electrical conductivity of 



fluorescent substances, Physical Review, vol. 19, p. 396. 



5. The luminescence of sidot blendes. Physical Review, vol. 21, p. 247. 



Experiments upon the influence of red and infra-red rays upon 

 the luminescence of sidot blende are in progress and the results will 

 form the subject of the sixth of our series of papers. Orders have 

 been placed for special apparatus for the study of the cathodo- 

 luminescence of various substances. Most of this apparatus has 

 already been received, and it is proposed to begin this portion of the 

 work immediately upon the completion of the experiments on the 

 influence of the infra-red ravs. 



