OF ARTS AND SCIENCES, 149 



» 



inal manuscripts of Lalande, at the request of Leverrier. He 

 had found that the doubtful marks of the printed copy were not 

 contained in the original record ; and that there was an obser- 

 vation of the planet of May 8, 1795, which was not published. 

 More than fifty years ago, then, Lalande had in his possession 

 observations enough of Neptune to have discovered it ; and 

 he could not have failed to make this discovery if he had 

 taken reasonable pains to satisfy himself as to the discrepant 

 character of the observations by a new comparison with the 

 stars. 



Professor Peirce stated that he had compared the observa- 

 tion of May 8, 1795, with Mr. Walker's orbit, and found it to 

 be perfectly consistent with the slight changes which are re- 

 quired to satisfy the observation of May 10, 1795. Mr. Walk- 

 er's orbit cannot, therefore, differ much from the exact orbit, 

 and there can be no important error in adopting it as the basis 

 of further research. The period is very near the double peri- 

 od of Uranus, but yet it seems to differ too much from this 

 double period to admit of the establishment of a libration 

 about that period. The principal effect of Neptune upon Ura- 

 nus must, in case of the failure of this double period, be ex- 

 hibited in the manifestation of an equation of the centre differ- 

 ent from that which belongs to the proper elliptic motion, so 

 that Uranus will have two equations of the centre, one of 

 which will belong to its ellipse, and the other to the attraction 

 of Neptune. 



James D. Dana, Esq., Corresponding Member of the Acade- 

 my, presented (through the Corresponding Secretary) a paper 

 comprising brief characters of the Crustaceas collected in the 

 United States Exploring Expedition under Captain Wilkes, 

 as follows : — 



Conspectus Crustaceorum^ in orbis terrarum circumnavigatione, C. 

 Wilkes e classe Reipublicce Fcederatce duce, colleciorum auctore 

 J. D. Dana.* 



* Conspectus narrationis uberioris auctore auctoritate publicd edendae. 



