SECT, vni.] ASTRONOMICAL TABLES. 71 



were eliminated, or got rid of, and there only remained a 

 relation between the mass of the new planet and three of the 

 elements of its orbit ; and it then was necessary to assume 

 such a value for two of them as would suit the rest. That 

 was accomplished so dexterously, that the perturbations of 

 Uranus were perfectly conformable to the motions of Nep- 

 tune, moving in the orbit thus found, and the place of the 

 new planet exactly agreed with observation. Subsequently 

 its orbit and motions have been determined more accu- 

 rately. 



The honour of this admirable effort of genius is shared 

 by Mr. Adams and M. Le Verrier, who, independently of 

 each other, arrived at these wonderful results. Mr. Adams 

 had determined the mass and apparent diameter of Neptune, 

 with all the circumstances of its motion, eight months be- 

 fore M. Le Verrier had terminated his results, and had also 

 pointed out the exact spot where the planet would be found ; 

 but the astronomers neglected to look for it till M. Le 

 Verrier had published his researches, and assigned its place 

 to Dr. Galle, at Berlin, who found it the very first night he 

 looked for it, and then it was evident that it would have 

 been seen in the place Mr. Adams had assigned to it eight 

 months before had it been looked for. So closely did the 

 results of these two great mathematicians agree. 



Neptune has a diameter of 43,000 miles, consequently he 

 is about 200 times larger than the earth, and may be seen 

 with a telescope of moderate power. His motion is retro- 

 grade at present, and six times slower than that of the 

 earth. At so great a distance from the sun it can only 

 have the rJooth part of the light and heat the earth receives ; 

 but having two satellites, and like Saturn being encom- 

 passed by a ring 64,500 miles in diameter, the deficiency 

 of light may in some measure be supplied. 



The prediction may now be transferred from Uranus to 

 Neptune, whose perturbations may reveal the existence of a 

 planet still further removed, which may for ever remain be- 



