the movements of Jupiter and Saturn, although in reality, as Laplace afterwards proved, that peculiarity was a necessary consequence of relations already known to exist between these two planets. Now, only conceive how enormously difficult the converse problem must be when the direct problem is so difficult. If when we take two known planets of given mass, distance, and so on, we find it extremely difficult to determine in what way each planet will affect the other, how exceedingly difficult-might we not even imagine, how utterly impossible-it must be to infer from the peculiarities of motion of one planet the distance, mass, and position of a planet hitherto unknown! This was the problem which lay before astronomers, and all save two shrank from the attempt to solve it. Of these two one was a young man who was preparing to take his degree at Cambridge-John Couch Adams, destined to be soon regarded as the greatest mathematical astronomer England has had since Newton's day. The other was the Frenchman Leverrier, Adams's senior in years, possessed of far more complete information of the facts of the case, and of far more abundant leisure to deal with the problem.

Young Adams first completed his work. He estimated the place of the as yet unseen planet, and announced it to the Astronomer Royal for England. Challis also, the head of the Cambridge observatory, received the news. Between these two observatory chiefs it might be thought that the new planet, if it lay anywhere near the indicated place, would be quickly discovered. But Professor Airy

seemed to imagine that a mare's nest had been discovered. He put some questions intended to be posing, which the young Johnian was not eager to answer. Challis was more zealous in the cause of science. He did all he could be expected to do, especially when we remember that he quickly learned that the Astronomer Royal had small faith in the superior mathematical power of his young contemporary. It may perhaps surprise some readers to learn that Challis actually saw the planet. He saw it twice, and each time marked its place. The planet was in the net. Nothing, it should seem, could lose England the credit of the greatest astronomical feat since Newton's day. But, to quote an old proverb, the cards never forgive. The Astronomer Royal had challenged ill fortune for England, and ill fortune came. It was in September 1845 that Adams had communicated to Challis the place of the disturbing planet, and in October that in the pleasing confidence of youth he had forwarded the information to the Astronomer Royal.

In June 1846, or fully eight months after Adams's first intelligence, Leverrier assigned,' to use Challis's words, 'very nearly the same longitude for the probable position of the planet as Mr. Adams had arrived at.' But even then the information Leverrier gave was not so complete as that which Adams had given, for Adams stated the form and position of the orbit, the mass, and the mean distance of the hypothetical planet, whereas Leverrier 'gave no results,' says Challis, respecting the planet's mass and the

form of its orbit.'

Shortly after the Astronomer Royal

began to think that possibly Adams might after all be right. But it was now too late. For the Berlin astronomers, six weeks after Challis had secured two observations of the planet, detected it from Leverrier's announced place. It is only necessary, to make the story complete, to mention that as soon as Challis, Sir John Herschel, and others announced what Adams had really effected, Arago and other French astronomers abused our great young Englishman as an interloper, as though it were incredible that the country of Newton should have produced the equal of Leverrier.

I must not dweil further, however, on the circumstances of this discovery, preferring to deal with the pleasanter considerations suggested by its nature. It seems to me in some respects even more striking than Newton's discovery of the law of gravitation. Newton explained the laws according to which known objects move; Adams and Leverrier showed where a hitherto unknown object would be found when telescopes were turned to that part of the heavens. Newton recognised laws. hitherto unknown. Adams and Leverrier by abstract reasoning inferred the existence of a world which men as yet had never seen.

But there is one consideration which is even more suggestive. The acutest reasoners among men have been able to detect a planet by means of the disturbances produced by its attraction acting on the planet which travels

nearest to it. But if the mental powers of man were increased he could analyse disturbances much more minute in their effects. We can conceive so great an increase of power that, from the motions of one planet only, the nature of the whole solar system might be inferred. But to the infinite wisdom of the Almighty a power of inference such as this is as the weakness of the infant's mind compared with the powers of a Newton. To Him the least grain indicates the whole scheme of the universe, its present condition, past history, and future fate. Not an atom in the remotest orb can move a hair's breadth without producing in every other atom throughout the universe an effect-infinitely minute to our perceptions— but as manifest to the Almighty as the noon-day sun to Man reaches the limit of his powers in reasoning from one planet to the next; to the Almighty every atom in infinite space is eloquent of the universe itself.

us.

THE LOST COMET.

And I looked, and behold, a great cloud came out of the north, and a fire enfolding itself, and a brightness was about it, and out of the midst thereof as the colour of amber, out of the midst of the fire.-EZEKIEL i. 4.

THESE words describe, not inaptly, what was seen on the evening of November 27, 1872, in Italy and other countries where the atmosphere was clear. Here in England there was a display of shooting-stars, some forty or fifty thousand of these bodies falling between the hours of five and eleven. But wonderful as was this display, in Italy a yet more unusual spectacle was witnessed, for at the height of the display the smaller meteors were so numerous that the appearance presented was that of a cloud of light around the gemmed feet of Andromeda in the northern skies;

a great cloud came out of the north, and a fire enfolding itself, and a brightness was about it.' Moreover, since the larger meteors shine for the most part with a yellowish light, it may be said that 'out of the midst of the cloud came a brightness as the colour of amber, out of the midst of the fire.'

Soon after it was announced that the meteors forming this wonderful display were travelling on the track of a