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Cuar. IT.,§5.] PHYSICAL ASTRONOMY.—M. LEVERRIER—MR ADAMS. 831 
before it was at Berlin, M. Leverrier must still have stant lowered the dignity of his position by one 
had a share in the credit of success. ungenerous expression,—but that the absolute merit 
(141.) It is perhaps to be regretted that Mr Adams had of both is of the very highest character is on all 
Remarks ot given his whole investigation to the world, or hands admitted. ‘The names of M. Leverrier and 
oo his- ot least published his results, so as to avouch the Mr Adams,” said Sir John Herschel, addressing the 
: confidence which he felt in his own prediction, and Astronomical Society, “ which Genius and Destiny 
to throw upon practical astronomers generally the re- have joined, I shall by no means put asunder ; nor 
sponsibility of its verification. Had he done so in will they ever be pronounced apart so long as lan- 
1845, it is possible that the planet might have been guage shall celebrate the triumphs of Science in her 
discovered at the opposition of that year; but it is at sublimest walks.” 
least certain that M. Leverrier’s claims to priority But before closing, I must briefly state how far roe 
as regards the discovery of Neptune would have the orbit of the planet Neptune, when discovered, ior ag 
been effectually anticipated. Butitis only just to our realized the previsions of theory. A fortunate cir- Neptune as 
countryman to recollect the difference of his age and cumstance rendered it easy to obtain at an early ® fixed star. 
position. M. Leverrier was at the time about 35 period a correct knowledge of the elements. It seems 
years of age, and was a candidate for the sub- that the planet Neptune was observed by Lalande at 
stantial benefits as well as for the honour of a mem- Paris on the 8th and 10th May 1795, and entered 
bership of the Academy of Sciences. Mr Adams as a fixed star, notwithstanding a distinct change of 
must have been nine or ten years younger at the place between the observations, actually corresponding 
period of this discovery, a circumstance which en- to what the planet should have had.1_| But such an 
hances our admiraion at the achievement, whilst it oversight had been made by Lemonnier in the case 
gives an additional grace to the modest conduct of of Uranus. By means of this observation of fifty 
the author. years back, the orbit was easily computed. It is a 
(142,) I have endeavoured to state correctly (with due re- singular and startling fact, that, except as regards the 
gard to the limits of this essay) the main facts of the longitude on the orbit, the other elements computed 
most curious case of double discovery which, perhaps, from observation were somewhat widely different 
the history of science presents; and happily as tothe from those assigned by M. Leverrier and Mr Adams. 
facts, down to the minutest detail, no discrepancy of We shall present them inatabular view. The value 
opinion ever existed. Different minds will, with per- of the mass in the last column is calculated from the 
fect truth, attach more or less distinction to the two elongation and period of a satellite of Neptune dis- 
illustrious rivals,—neither of whom has for an in- covered by Mr Lassell. 
Theory—Leverrier. Theory—Adams, Observation— Walker. 
Epoch of Elements, . . 1st Jan. 1847, 6th Oct. 1846, 1st Jan. 1847. 
ean Longitude, eo x. 318° 47’ 323° 2’ 328° 33° 
Mean Distance, . . . 36°15 37°24° 30°04 
Doriod,. | submits ata: 217-4 years 164:6 
Long. Perihelion, ‘ f 284° 45° 299° 11’ 47° 12’ 
Excentricity, pte 0°1076 0-1206 0-00872 
Mass, . 3 ‘ 7 ue'ey of Sun’s eres rsies* 
(144.) The differences of theory and observation are so_ sible therefore only twenty years before conjunction. 
striking as to have occasioned surprise to many per- In this time Neptune describes (really) only 4 of a cir- 
sons that, with data so erroneous, the perturbations cumference, or 45°, and relatively to the motion of 
of Uranus or the longitude of Neptune at the epoch Uranus about the same. It is evident then that 
of discovery should have been obtained even approxi~ even a considerable error in the period of Neptune 
mately, would scarcely sensibly affect the law of perturba- 
(145.) The fact, however, is this :—that the mutual per- tion during twenty years, and that the approximate 
How an as- turbations of Uranus and Neptune are sensible for determination of the place of the perturbing planet 
= sonal only a small portion of the joint orbits when the about the time of conjunction will not be much 
elements planets are nearly in conjunction. The conjunction affected by the error of that assumption. Again, 
led to the (when the mutual distance is least and the attraction as to the error of mean distance, we may observe, 
~ nolan strongest) took place in 1822. Now the places of that since the mutual action of the planets is 
Uranus from 1690 (the first observation) until 1800 confined within such (comparatively) narrow limits 
can be sufficiently well represented by elliptic ele- of space and time, though we might anticipate a toler- 
ments. The perturbation of Neptune became sen- able approximation to the interval between the bodies 
1 One of the observations was suppressed in the publication, and only discovered on searching Lalande’s MS. 
2 This was the hypothesis upon which Mr Adams made his second or corrected calculation of elements. Nevertheless, he 
inferred from that calculation that the mean distance might with much probability be reduced to 33-4, 
% Pierce, Struve’s mass is yz}q5- ; 
