88 RECORDS 



SECTION OF ASTRONOMY, PHYSICS AND 

 CHEMISTRY. 



January 7, 1901. 



Section met at 8:20 P. M,, Professor William Hallock pre- 

 siding. 



The minutes of the last meeting of Section were read and 

 approved. 



The following program was then offered : 



Harold Jaooby, A New Telescope for Photographing 

 THE Pole of the Heavens. Illustrated. 



Geo. B. Pegram, Reflection of Light from White Sur- 

 faces. 



Professor Jacoby announced that this plan of photographing 

 the close polar stars had made material progress. A special 

 instrument has been constructed and mounted at the observa- 

 tory at Helsingfors, Finland. Photographs of the actual instru- 

 ment in position for use were exhibited. It is planned to make 

 photographs with this instrument in which the close polar stars 

 will trace out " trails " on the plate corresponding to their diur- 

 nal motion. The effects of refraction, etc., having been elimi- 

 nated by computation, it is possible to obtain from such photo- 

 graphs the exact position of the celestial pole among the 

 stars and on the date of observation. The intercomparison of 

 results taken on dates six months apart should furnish a new 

 determination of the constant of aberration, and photographs 

 taken annually throughout a series of years should determine 

 the constant of nutation and ultimately perhaps even that of 

 precession. 



The actual observing with the instrument will commence in 

 the spring as soon as the Helsingfors astronomers have fin- 

 ished with the observations of Eros now in progress, and the 

 plates will be sent to Columbia University, New York, for 

 measurements and reductions. An outline of the method to be 

 used, together with a preliminary trial of the same, has already 

 been published by Professor Jacoby under the title '* Photo- 

 graphic Researches near the Pole of the Heavens," Bulletin of 



