physics. 389 



In collaboration with Professor Bridgman, of Harvard, she has also made 

 an important study of the action of high pressures, up to 3,500 atmospheres, 

 upon the absorption spectra of various substances, with results by the use 

 of which it will be possible to compare definitely the effects of pressure with 

 those of cooling. 



Dr. Tanaka is engaged in a detailed spectro-photometric study of sub- 

 stances whose kathodo-luminescence depends on the presence of traces of an 

 activating element such as copper, manganese, lead, bismuth, zinc, or silver. 

 He has confirmed Dr. Howes's discovery that the spectra of such compounds 

 (a class which includes the Lenard and Klatt sulphides, the commercial phos- 

 phorescent sulphides of zinc and of calcium, etc.), although they appear to 

 the eye to consist of one or two very broad bands covering the greater part 

 of the visible spectrum, are really made up of numerous, equidistant, over- 

 lapping components. 



Dr. Tanaka finds furthermore that the position and interval of the components 

 depend only on the activating material and are the same whatever the solid 

 solvent and flux; also that there is a perfectly definite relation between atomic 

 weight and interval such that activating elements, when unknown, can be 

 identified from the interval. 



Miss M. A. Ewer is making a detailed mathematical study of the structure 

 of flame spectra with special reference to the question of the series of constant 

 frequency intervals. She has developed a graphic method based on the 

 doctrine of congruences, by which it will be possible to determine whether 

 such intervals as are found by other methods show real or only apparent series. 



She finds that the numerical relation is one of rather close approximations, 

 not of absolute values; but that, despite this fact, the grouping is real for some 

 at least of the elements giving a flame spectrum. Other elements are still 

 under investigation. 



The intervals so far found, both in the investigations of Dr. Tanaka and 

 those of Miss Ewer, are related inversely to the atomic numbers of the 

 elements. 



Mr. D. T. Wilber has been engaged throughout the year in the study of 

 the very intricate and puzzling question of the effects of heat-treatment on 

 the activity of various luminescent compounds. Dr. H. Kahler is investigating 

 the equally difficult problem of the relations of photo-electric properties to 

 luminescence. 



