134 



Scientific Intelligence. 



Comparison with Lalande's Observations. 



Bate, 1795. 

 Mean time, Paris. 



Lalande's two observations of Neptune. | Ep?i7me^ilVlI. 



R. A. 



May 8 th 

 May 10th 



h, m. s. 



11 10 57 



11 2 55 



Observed motion in two days, 

 Computed do. Elements VI I , 



Discrepancy, . . 



213° 41' 3' '-89 

 213 38 5 -16 



178"- 73 

 185 -42 



t>"-6!> 



Dec. 



South J 1° 35' 4"-96 

 South 11 34 5 -64 



~~ 59"-32 



62 -38 



R. A. 



Dec. 



3"-06 



-f-141"-l+39''-5 

 + 147 -8 + 36 -4 



The small difference of three minutes of arc between theory and 

 observation for 1795, may be ascribed to the perturbations for that date, 

 and for the fifty-two years' interval, which have been neglected. 



The tropical period falls short by nearly a year of that which Profes- 

 sor Peirce has pointed out as necessary, in order that the Laplacian 

 Libration should take effect. It is quite possible that a more full dis- 

 cussion of the perturbations may show the necessity of the Libration. 



The eccentricity of Venus is 0*007, the smallest before known; that 

 of Neptune is 0-005. 



Hence it appears that the orbit of Neptune approaches nearer to a 

 perfect circle than that of any other planet. I regard this value of 

 the eccentricity of Neptune as conclusively established, and with this 

 view will quote from LeVerrier's communication made to the Institute 

 of France on the 29th of March last on the occasion of announcing 

 my discovery. M. LeVerrier remarks : 



" We confine ourselves for the present to the remark that this small- 



SFwii eccentricit y> which w ould result from the calculations of 

 M. Walker, would be incompatible with the nature of the perturba- 

 tions of the planet of Herschel. But it may be that this smallness of 

 eccentricity is not a necessary consequence of the representation of 

 Lalande s observation." 



While I feel myself honored by the notice taken of my labors by the 

 French astronomers, I think it just to express my full belief that when 

 they have bestowed on its present orbit the same pains as myself, they 

 will agree with me that this smallness of eccentricity is an unavoidable 

 consequence of the direct observations. 



If we admit for the moment that my views are correct, then LeVer- 

 rier's announcement of March 29th is in perfect accordance with that 

 of Professor Peirce of the 16th of the same month, viz. that the pres- 

 ent visible planet Neptune is not the mathematical planet to which 

 * - ' •■ None of its elements conform to 



Nor does it perform the functions on which 

 alone its existence was predicted, viz. those of removing that oppro- 

 brium of astronomers, the unexplained perturbations of Uranus. 



We have it on the authority of Professor Peirce that if we ascribe to 

 Neptune a mass of three-fourths of the amount predicted by LeVerrier, 

 it will have the best possible effect in reducing the residual perturba- 

 tions of Uranus below their former value ; but will nevertheless leave 

 them on the average two-thirds as great as before. 



It is indeed remarkable that the two distinguished European astrono- 

 mers, LeVerrier and Adams, should, by a wrong hypothesis, have 

 been led to a right conclusion respecting the actual position of a planet 



theory had directed the telescope, 

 the theoretical limits. 



