202 PKOCEEDINGS OF THE AMERICAN ACADEMY 



CompositsB, detected by Mr. Charles Wright in the Eastern 

 Part of Cuba. 



II. On the Genus Croomia, and its place in the Natural 

 System. 



Four Iiuuclred and sixty-fiftli meeting. 



April 26, 1859. — Supplementary Meeting. 



In the absence of the President and Vice-President, the 

 Corresponding Secretary took the chair. 



The Corresponding Secretary read a letter from the Asiatic 

 Society, dated Calcutta, December 10, 1858, acknowledging 

 the receipt of the Academy's publications. 



Professor Peirce gave the following analysis of his memoir 

 upon the Tail of Donati's Comet. 



" 1. The theory proposed by Bessel, in Vol. XIII. of the Astrono- 

 mische Nachrichten, is adopted as the basis of the theory, and it is 

 proposed to determine the special values of the repulsive force from 

 the sun, and of the initial impulse given by the comet, which are most 

 reconcilable to the observed phenomena. In the first approximation, 

 the initial impulse was neglected, because it was assumed to be quite 

 small. 



" 2. Rigorous formulfe are adopted in place of the approximations 

 given by Bessel, which are only available at a short distance from the 

 head of the comet, whereas the critical portions of the investigation 

 are those which apply to the part of the tail which is most remote from 

 the head. The approximate formula were employed by Pape in his 

 researches upon Donati's comet, which is astronomically designated as 

 1858 V. 



" 3. The observations of the tail which have served as the basis to 

 this investigation are those given by Pape in the Astronomische Nach- 

 richten, and an admirable series made at the Dudley Observatory, by 

 Mr. Searle and Mr. Toomer, under the judicious direction of Dr. 

 Gould. 



" 4. The observations of the front edge of the Donati comet are 

 very well satisfied by a solar repulsive force = — \^, if gravity is 

 adopted as the unit of force. The comparison of theory with observa- 



