241 



of the Work under his charge, during the year ending Novem- 

 ber, 1845. 8vo. — From Prof. A. D. Bache. 



Eighth Geological Report to the Twenty-sixth General Assembly 

 of the State of Tennessee, made November 1st, 1845. By G. 

 Troost, M.D. — From the Author. 



The Oregon Question. By Albert Gallatin. New York, 1846. 

 8vo. — From the New Yorlc Historical Society. 



ADDITION TO THE LIBRAKY BY PURCHASE. 



Astronomische Nachrichten. No. 551. 4to. 



The Committee, consisting of Mr. A. D. Bache, Dr. R. M. 

 Patterson, and Mr. T. M'Ewen, on the paper of Mr. Nulty, 

 entitled, "On the Determination of Azimuths by the Star Po- 

 laris," reported in favour of publication, which was accord- 

 ingly ordered. 



Dr. Bache informed the Society of the death, on the 4th of 

 March, of Mr. Joseph Reed, aged 73. 



Mr. Peale offered, for the examination of members, a speci- 

 men of the flexible granular quartz referred to at the last meet- 

 ing. 



Prof. Kendall read a letter from Prof. Stephen Alexander, 

 suggesting for consideration the following hypothesis, to ac- 

 count for the peculiarities in the appearance of Von Biela's 

 comet. It supposes a partial change to have taken place simi- 

 lar to that which, according to Sir John Herschell, would seem 

 to have been experienced by Halley's comet about the time of 

 its perihelion passage in 1835. 



The central portion of Von Biela''s comet has been transformed 

 into invisible vapour, and the portion designated by Lieut. Maury 

 as '^^Biela" seems to be more sensitive to such a change than ^^ No. 

 2." The progress of this change would seem to account for — 



1st. The apparent rupture of the comet. 



2d. The seeming recess of tlie two portions, as observed by Mr. 

 Walker. 



3d. The comparative decay of "Biela" observed by Lieut. Maury. 



4th. The comparative increase of the same since the perihelion 

 passage, observed by the same astronomer. 



5th. The Hght arch of cometary matter mentioned in Lieut. Mau- 

 ry's account of his observation, Feb. 19th. 



VOL. IV. — 2 I 



