RECORDS 89 



the Imperial Academy of Sciences of St. Petersburg, 5th Series, 

 Vol. 9, p. 41, 1898, June. 



The second paper presented the results of an experimental 

 study of some white surfaces with regard to the relation between 

 the intensity of the reflected ray and the angles of incidence and 

 reflection. It was carried out by means of a special photometer 

 allowing the use of any desired angles of incidence and reflec- 

 tion. Among the surfaces tested were plaster of Paris, several 

 kinds of unglazed paper, compressed powders of several kinds, 

 powders not compressed, but gently smoothed with a metal 

 plate, and finally a surface made by allowing fine plaster dust 

 to settle from suspension in the air on a suitable plate. These 

 surfaces in the order named showed decreasing polarization of 

 the reflected light, and less approach to specular reflection. The 

 fine dust surface showed no polarization and almost no tendency 

 to regular reflection. The results with this surface as shown 

 by sets of curves, follow pretty closely the old Lambert's or 

 cosine law. 



Intensity = A cos / cos r. 



with some departure when both angles were very large. With 

 all the other surfaces the departure was very great for angles 

 greater than 70°. Contrary to the results of Mr. Wright {Phil. 

 Mag., Feb., 1900) these experiments were quite in accord with 

 the demand of theory that the intensity of the reflected ray 

 should be expressed as a symmetric function of the angles of 

 incidence and reflection. 



William S. Day. 



Secretary. 



SECTION OF BIOLOGY. 



January 14, 1901. 



Section met at 8:15 P. M., Professor C. L. Bristol presiding. 



The minutes of the last meeting of Section were read and 

 approved. 



The name of one candidate for resident membership was read 

 and referred to the Council according to the By-Laws. 



