LETTER 



FROM 



LIEUTENANT C. H. DAVIS, 



SUPERINTENDENT OF THE NAUTICAL ALMANAC, 

 TO 



JOSEPH HENRY, LLD., 



SECRETARY OF THE SMITHSONIAN INSTITUTION. 



Sir : With the permission of the Hon. Secretary of the Navy, I have the 

 pleasure to forward to you for pubhcation Mr. Walker's Ephemeris of the Planet 

 Neptune for 1851, prepared at my request for the Nautical Almanac. 



The comparison of the Ephemeris of 1850 with observations confirms Mr. 

 Walker's experience of 1848 and 1849, showing that no change can be made in 

 the basis of the Ephemeris for 1851. The latter, therefore, is an extension 

 merely of that of 1850 by Mr. Walker's elements^'^ and Professor Peirce's 

 theory. ^^' 



The numerical values of the perturbations of Neptune's elliptical true longi- 

 tude and radius vector, are given by Professor Peirce up to the date of January 

 I, 1851, as computed from the pi'imitive formulae for the inequalities. They 

 have been extended by Mr. Walker to January 1, 1854, by using the tables in 

 their modified form, as follows :'^' 



(') Proceedings of the American Academy for April 4, 1848. 

 n Ibid, December 7, 1847. 



(^) See page 9th of Prof. Peirce's Memoir, ibid. On page 12th, in the first line of the value of Jl, for 311° read 221°: 

 also, in the first line for the value of B, for — 0.00066 read + 0.00127. 



