386 PROCEEDINGS OF THE AMERICAN ACADEMY 



qualities of cheapness, portability, great stability, and most ac- 

 curate and delicate adjustment were combined. 



Pour Iiundred and thirty-nintli meetiug^. 



May 12th, 1857. — Monthly Meeting. 



The Academy met at their rooms. Professor Tread well, 

 Vice-President, in the chair. 



The Correspo''"^ing Secretary read letters from the Ethno- 

 logical Society, London ; the Royal Saxon Society of Scien- 

 ces, Leipsic ; the Royal Bavarian Academy of Sciences, Mu- 

 nich ; and the Boston Society of Natural History, acknowl- 

 edging the receipt of the Academy's publications ; and from 

 the Royal Bohemian Society of Science, Prague, presenting 

 its Transactions. 



Mr. G. P. Bond communicated the results of an examina- 

 tion of the photographs of the star Mizar (^ Ursa Majoris), 

 with its companion, and the neighboring star Alcor ; speci- 

 mens of which were exhibited. 



" Daguerreotype images of the star Vega (« Lyrse) were obtained 

 at the Observatory of Harvard College by the well-known artist, 

 Mr. J. A. Whipple of Boston, on the 17th of July, 1850, and subse- 

 quently impressions were taken from the double star, Castor, exhibit- 

 ing an elongated disc, but no distinct separation of its two compo- 

 nents. These were the first, and, till very recently, the only known 

 instances, of the application of photography to the delineation of the 

 fixed stars. 



" A serious difficulty was interposed to further progress by the 

 want of suitable apparatus for communicating uniform sidereal motion 

 to the telescope. This has now been supplied by replacing the origi- 

 nal Munich clock of the great equatorial of the Observatory by a new 

 one, on the principle of the spring governor, invented by the Messrs. 

 Bond. This clock, which was made by Messrs. George and Alvan 

 Clark of East Cambridge, carries the telescope with admirable even- 

 ness and regularity of motion. 



" Immediately upon its completion, at the invitation of the Director 

 of the Observatory, Messrs. Whipple and Black commenced a new 

 series of experiments, and have succeeded in transferring to the plate, 



