OF ARTS AND SCIENCES: FEBRUARY 14, 1871. 309 



Life of Rumford be presented to Dr. George E. Ellis, together 

 with a complete set of the Essays (as edited by the Committee), 

 with the thanks of the Academy. 



It was voted that the Finance Committee be requested to 

 prepare a statement of the current expenses and receipts of the 

 Academy. 



It was voted that the meeting adjourn, at its close, to the 

 second Tuesday in March. 



Professor Pickering made a communication on a new form 

 of solar eyepiece, by which the light may be reduced to any 

 desired extent. 



In the common diagonal eyepiece all the light is reflected into the 

 eye by the inclined surface of the prism. A second prism is connected 

 to the first by some substance whose index of refraction is very nearly 

 equal to that of the glass. In consequence, an exceedingly small pro- 

 portion of the light is reflected, the greater part passing directly through, 

 out of the telescope. Again, since the angle of incidence equals 45°, 

 the reflected ray is almost totally polarized, and its intensity may be 

 varied at will by a Nicol's prism. Colored glasses are thus avoided, 

 and with them the danger of heating and cracking the lenses of the 

 eyepiece, as almost all the heat and light passes out of the tube. If 

 desired, it may be received on a second eyepiece or spectroscope, so 

 that during an eclipse or transit, for instance, two observers may use 

 the same telescope. A curious coloration of the images is sometimes 

 produced, probably due to the unequal dispersion of the glass and 

 cement. Apart from its practical application, this device has a scien- 

 tific interest as affording a means of producing a plane reflecting sur- 

 face whose index of refraction is very nearly unity. 



Professor J. D. Whitney read several affidavits of the dis- 

 covery of pre-historic man in Colorado. 



Professor N. S. Shaler made a communication on the forma- 

 tion of continents. He compared the circular development in 

 the Moon with the linear development in the Earth and Mars. • 



Professor J. D. "Whitney read letters from Baron Richtofcn 

 on the geology of China and Japan. He also exhibited a new 

 method of illustrating books. 



