356 RROCEEDINGS OF THE AMERICAN ACADEMY. 



could be used as a photometer and such cells of which I have one 

 at the Institute of Technology were put upon the market. They 

 did not prove however, to be of practical value since their indica- 

 tions were uncertain and the results unreliable. 



" A few years since however, Professor Stebbins undertook a new 

 investigation of the selenium cell with a view to its applications 

 to stellar photometry. By a most careful and painstaking in- 

 vestigation, he was able to discover the necessary conditions of 

 success, finding among other things, that the cell must be kept at a 

 low temperature. 



" As a result of these investigations, he finally succeeded in con- 

 structing a stellar photometer of exquisite sensitiveness, the 

 accuracy of whose results much exceeded those given by visual 

 observation. 



" He has applied the instrument to the study of the light varia- 

 tions of variable stars. In one case, that of the well known 

 variable Algol, the "light curve" determined with the selenium 

 photometer showed a secondary minimum which had not been 

 detected by visual observation. He has also applied the instru- 

 ment to the study of short period spectroscopic binaries with very 

 important results. By the same method, he has detected and 

 studied the variations in brightness of the pole star." 



The President then presented the Medals to Professor Stebbins, 

 who responded, giving a brief account of his researches. 



In stating the grounds for the award of the Rumford Medals to 

 Dr. William David Coolidge, Professor Cross said in part, "At its 

 last Annual Meeting, May 13, 1914, the Academy acting on the 

 recommendation of the Rumford Committee, voted to award the 

 Rumford Premium to William David Coolidge for his invention 

 of ductile tungsten and its application in the production of radia- 

 tion. 



" Lamps with carbon filaments were the standard form for many 

 years. The efforts of inventors were unremitting however, to 

 secure a filament which should stand the strong current and high 

 temperature needed to give a satisfactory white light and espe- 

 cially a higher efficiency in operation. 



" Wires of tantalum gave quite satisfactory results but the sub- 

 stance tungsten seemed to possess certain advantages. It was 



