This was the problem he set himself to work upon, by the means of solving the inverse problem of the perturbations; for instead of having to measure the action of a determined planet, he had to deduce the elements of the orbit of the disturbing planet, and its place in the heavens from the recognised inequalities of Uranus. And this problem M. Le Verrier has successfully solved. In his second paper he deduces the place in the heavens that the body must be as 325° of helio-centric longitude. On the 31st August last he published his third paper. In this he has calculated that the period of the planet is 217 years; and that it moves in an orbit at the distance of more than 3,000 millions of miles from the Sun; that its mean longitude on January 1st, 1847, will be 318° 17′; its true longitude 326° 32′; and that the longitude of its perihelion will be 284° 45′; that it will appear to have a diameter of 3¹⁄₄ seconds of arc as seen from the earth; and that it is now about 5° E. of _Delta Capricorni_. “These remarkable calculations have pointed out a position which has very nearly proved to be the true one. “On September 23, Dr. Galle at Berlin discovered a star of the eighth magnitude, which has proved to be the planet. Its place at the time was five degrees from _Delta Capricorni_. It was found to have a disc of 3 seconds as predicted; and its longitude at the time differs less than a degree from the longitude computed from the above elements. Its daily motion, too, is found to agree very closely with the predicted; and, judging from this last circumstance, the planet’s distance, as stated above, must be nearly the truth. “Thus the result of these calculations was the discovery of a new planet in the place assigned to it by theory, whose mass, distance, position in the heavens, and orbit it describes round the Sun, were all approximately determined before the planet had ever been seen; and all agrees with observations, so far as can at present be determined. It is found to have a disc, and its diameter cannot be much less than 40,000 miles, and may be more; its motions are very slow; it is at present in the constellation of Aquarius as indicated by theory; and it will be in the constellation of Capricornus all the year 1847. It may be readily seen in a telescope of moderate power. “Whatever view we take of this noble discovery it is most gratifying, whether at the addition of another planet to our list; whether at the proving the correctness of the theory of universal gravitation; or in what view soever, it must be considered as a splendid discovery, and the merit is chiefly due to theoretical astronomy. This discovery is perhaps the greatest triumph of astronomical science that has ever been recorded.”[33] [33] “Illustrated London Almanack for 1847.”