LETTER 



FROM 



LIEUTENANT C. H. DAVIS, 



SUPERINTENDENr OF THE NAUTICAL ALMANAC, 



JOSEPH HENRY, LL.D., 



SECRETARY OF THE SMITHSONIAN INSTITUTION. 



Sir : With the authority of the Hon. Secretary of the Navy, I have the plea- 

 sure to submit to you for publication the Ephemeris of the planet Neptune, for 

 the year 1850, prepared for the Nautical Almanac by Sears C. Walker, Esq. 

 This is a continuation of the Ephemeris of 1849, which appeared in Appendix I 

 to Vol. II, of the Smithsonian Contributions ; being based on the same theory, 

 elements, formulse, and constants, viz.. Prof Peirce's theory, and Mr. Walker's 

 elements, as originally published in the Proceedings of the American Academy 

 for April 4, 1848. 



In his introduction to the Ephemeris of 1848, Mr. Walker remarked, " Prof 

 Peirce's new theory of Uranus may now be considered as complete. That of 

 Neptune can hardly be expected to make fuilher advances till another opposi- 

 tion is observed." And in 1849, the opposition of 1848 having been in the 

 mean time observed and discussed, without indicating any sensible correction, 

 he added, " I have accordingly not attempted any change in the elements used 

 as the basis of the Ephemeris of 1849." 



The theory and elements have now been submitted to the test of a second 

 opposition, that of 1849, and Mr. Walker still finds that no sensible correction 

 is required in the basis of the Ephemeris for 1850. This result is as gratifying 

 as it is unexpected. It evinces the great care bestowed by Prof Peirce upon 

 his second essay to perfect the theory of Neptune, and the remarkable accuracy 

 with which the elements of Mr. Walker were determined, from data that could 

 never have been regarded as sufficient to furnish a complete orbit. 



