580 The Smithsonian Institution 



by Walker, was a genuine service to science by American 

 astronomy. 



A perusal of this and other works of Walker — and of those 

 of Coffin, Gould, Gilliss, Hubbard, Peirce, and others, his col- 

 leagues and contemporaries — will go far to exhibit to students 

 of the present generation how thoroughly American astron- 

 omy of fifty years ago was grounded in the classic methods 

 of Gauss, Bessel, and Struve. 



A very complete history of the discovery of Neptune, writ- 

 ten by Doctor B. A. Gould, was printed and distributed by 

 the Institution in 1850 as an octavo pamphlet. 



The "Contributions to Knowledge"^ in 1866 contains 

 an investigation of the orbit of Neptune and tables of its 

 motion, being the first publication of the long series of 

 such researches which are owed to Professor Newcomb. 



The theory of Neptune had previously been investigated 

 by Peirce and Walker in America, and by Kowalski and 

 Wackerbarth in Europe. But in 1863 the difference between 

 observation and calculation had risen to ^2!' ^^^ 22" in the 

 two coordinates, and the theory evidently required revision 

 in order to perfect the tables, on the one hand, to see if the 

 discrepancies might arise from a trans- Neptunian planet. 

 This is one of the four main problems proposed for solution 

 by the author, the others being a new determination of the 

 elements from the 40° already traversed by the planet in 

 its orbit ; a new determination of the mass of Uranus ; and the 

 construction of tables covering the dates from a. d. 1600 to 

 2000. 



The formuLne for perturbations are developed in chapter 

 II, and seven normal places from 1846 to 1863 are formed. 

 Lalande's observation of i 795 receives a new and careful re- 

 duction, which shows it to differ from the adopted theory by 



1 Volume x\% first paper. 



