Asironomy. ~ 129 
origin of the work which I have the honor to day to present to the Acad- 
emy.” He proceeds to state in general his investigations of all the known 
perturbing causes operating on Uranus, and his. determination of the 
actual amount of departure of Uranus from the places assigned by the, 
theory. 
-In his second communication to the Academy, (at the session of June 
1, 1846,) Le Verrier presents a history of the observations upon Uranus, 
and of the mode in which the tables of its motions have been constructed, 
and the errors which they involve; and a sketch of various hypoth- 
eses proposed to account for the inequalities of the motions of the planet. 
ce 
of an unknown planet disturbing Uranus, more plausible? After showing 
where this new planet cannot be situated, he arrives at this question—“ Is 
situated in the Ecliptic, at a mean distance double that of Uranus? And 
if so, where is this planet actually situated ? What are the elements of 
the orbit which it traverses?” As one result of a rigorous discussion of this 
question, he gives, as a first approximation, this momentous conclusion, 
that in assigning to the planet a heliocentric longitude of 325° for Jan. 
1, 1847, there cannot be an error of 10°. This assigned place he then 
promises to bring within narrower limits, by new computations. In re- 
capitulating the labors required by his undertaking, he adds—‘‘ The ex- 
istence of a planet hitherto unknown being thus established beyond a 
doubt, I have reversed the problem hitherto proposed in computing per- 
bations i 
been obliged to set out from the inequalities observed in Uranus, in order 
» deduce the elements of the disturbing body, to give the place of this 
planet in the heavens, and to show that its action perfectly accounts for 
| the apparent inequalities of Uranus.” i nga 
This remarkable prediction of the position of a planet hitherto entirely 
unknown, uttered with calm confidence by the mathematician in his t, 
seems received with faint faith even by the astronomical ob- 
stranger would have presented a plain disc, and would thus have instant- 
ly disclosed its true character. Or if, with a smaller instrument, its place 
had been carefully measured, the observation of the next morning would 
have shown its proper motion. |. oki ne Bag : 
On the Bist of August, 1846, Le Verrier, with implicit reliance on the 
truth of his computation, presents to the Academy, a memoir On THE 
PLANGT WHICH CAUSES THE ANOMALIES IN THE MOVEMENT OF Uranus,” 
with a determination of its mass, its orbit and its actual position, (Comp. 
Ren., xxiii, 428.) In this paper he gives the elements at which he had 
arrived, as follows : vbitcite tas hace MER 
-  Semi-axis major of the orbit, . |. 36154 
Period of sidereal zevolutionys i Jee Rees 
Ex ici 010761 
Long. of perihelion, QR4° 45! M. Eqx. 1847'°0 
‘Mean long. Jan. 1, 1847, 318 47 
3300 
J SS. 
Sxcoxp Senies, Vol. III, No. 7.—Jan., 1847. 17 
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