May 19, 1921 proceedings : philosophical society 239 



are depicted a tree and a house, beside a dam, is transformed by the change 

 in illumination into a winter scene, with ice and snow. In another, the 

 smoke screen from a battleship shows concealed a large American flag, and 

 the inscription, "Victory." The picture of an airplane bearing a cross, the 

 German insignia, shows up the concealed circle, insignia of the Allies. The 

 portrait of a lady is completely transformed by the red light, into a land- 

 scape, with a horse and man in the foreground. 



The explanation of these effects lies in the two kinds of paints that Mr. 

 Bittinger uses. Any pair of these pigments is very well color-matched in 

 daylight, that is, there are two dark greens, two light greens, two lavenders, 

 etc. But one pigment of each pair reflects a considerable amount of red 

 light, so that in red light one is a highlight and the other a shadow. In any 

 painting the two color-matched pigments are applied, side by side; but that 

 of high reflecting power in the red is so manipulated that a complete picture 

 in this kind of paint is produced which is visible as such only when the 

 ordinary pigments are darkened by the use of the red light. 



Experimental demonstrations of the above phenomena were made. The 

 spectral reflection curves of the several paints as determined at the Bureau 

 of Standards were shown by lantern slides. These curves have been pub- 

 lished in the Journal of the Optical Society of America, September, 1920, 

 p. 391. 



The third paper, by I. G. Priest, on A relation between color and spectral 

 distribution of light, was also illustrated with slides. 



In a study of colors of the same quality evoked by stimuli of different 

 spectral distributions the following rule has been found to hold : If any two 

 lights, however different in spectral distributions, evoke colors of the same 

 quality the wave lengths of the centers of gravity of their spectral distribu- 

 tions are coincident. 



This paper has been published in the Journal of the Optical Society of 

 America, September, 1920. 



The last two papers were discussed by Messrs. SilsbeE, Tuckerman, 

 White, Lloyd, Ferner, and Sosman. 



844th meeting 



The 844th meeting was held in the Cosmos Club, January 15, 1921, with 

 President Paris in the chair, and 58 persons present. 



The address of the evening was by the retiring President, Robert B. 

 Sosman, on The distribution of scientific information. 



The paper was discussed by Messrs. Pawling, C. A. Briggs, FernER, 

 White, Brooks, Crittenden, Humphreys, Wright, Williamson, Bur- 

 gess, Watson Davis, and others. It has been published in full in the 

 Journal of the Washington Academy of Sciences.'^ 



845th meeting 



The S45th meeting of^the Society was held in the Cosmos Club, January 

 29, 1921, with President Paris in the chair, and 47 persons present. The 

 following program was given : 



G. Breit: The distributed capacity of inductance coils. 



The distributed capacity of inductance coils affects their behavior in elec- 

 trical circuits. It changes the effective resistance and inductance of induc- 

 tance coils. It is important for the radio engineer to be able to predict from 

 the construction of the coil the influence of its distributed capacity. The 



» This Journal 11: 69-99. February 19, 1921. 



