234 



Stated Meeting, November 18. 



Present, twenty-six members. 



Mr. Du Ponceau, President, in the Chair. 



Letters were read: — 



From Prof. Peirce, of Harvard University, dated 10th Nov. 

 1842, acknowledging the honour done him by his election as a 

 member of the Society: — 



From Dr. Tidyman, dated Charleston, 12th Nov. 1842, in 

 relation to certain autograph letters presented by him to the 

 Society: — and 



From Mr. Bossange, bookseller, of Paris, dated 10th Oct. 

 1842, addressed to the Librarian, offering his services to the 

 Society. 



The following donations were announced: — 



FOR THE LIBRARY. 



Proceedings of the Academy of Natural Sciences of Philadelphia. 



Vol. I. Nos. 17, 18 & 19. 8vo. Philadelphia, 1842.— From 



the Academy. 

 Seven Autograph Letters, addressed to Dr. Tidyman by distinguished 



persons in Europe — -From Dr. Tidyman. 



Dr. Bache announced the decease, on the 26th ult., of Dr. 

 William R. Fisher, a member of the Society, aged 34 years. 



Mr. Lea made some remarks on the form and structure of 

 those univalve shells, known as turbinated and discoid shells, 

 and exhibited various species. 



He stated that he was aware ten or twelve years since that some 

 of the German mathematicians were engaged in the investigation of 

 their forms, with a view to determine species mathematically. Mr. 

 L. referred to the ingenious and learned papers of Prof. Mosely, 

 in the Philosophical Transactions and Philosophical Magazine, on 

 Conchiliometry, proving the conchospirai to be the logarithmic spi- 

 ral. It would be difficult to deny the truth of Prof. Mosely's conclu- 

 sion, that " to each particular shell is annexed a characteristic num- 

 ber, being the ratio of the geometric progression." A more accurate 



