The errors of the tables for ancient observations were taken from Bouvard's equations of condition; and for the modern observations, the errors were taken solely from the Greenwich Observations till 1830, after which they were taken from the Cambridge and Greenwich Observations, and those in various Numbers of the Astronomische Nachrichten. In this manner he obtained several solutions differing slightly from each other, by successively taking into account more and more terms of the series expressing the perturbations; and, in September eighteen hundred and forty-five, before leaving Cambridge, he placed in the hands of Mr. Challis* a paper containing numerical values of the mean longitude at a given epoch, the longitude of the perihelion, the eccentricity of its orbit, the mass, and the geocentric longitude for September thirty, eighteen hundred and forty-five, of the supposed disturbing planet, which he calls by anticipation "THE NEW PLANET,” “evidently showing," as Professer Challis justly observes, "the conviction, in his own mind, of the reality of its existence."

Having thus solved the great problem which had so long occupied his thoughts, Mr. Adams was anxious for the discovery of his new planet; and, with this very object in view, he communicated its geocentric longitude to Professor Challis, who possessed instruments capable of exhibiting a planetary disc, or of detecting the planet from its change of place among the stars which surrounded it. Mr. Adams was now entitled to consider his labours at an end. He had discharged all the duties of the Mathematician, and it remained for the practical astronomer to perform his part. He had discovered the planet in theory-it remained to be seen in space. He had seen it in his mind's eye, by the radiations of force with which it pursued its brother planet; it remained to be pictured on the human retina by its material emanations.

But Mr. Adams was not content with handing over his discovery to Professor Challis-to the inquisition of the Cambridge Transit Instrument, or to the scrutiny of the Northumberland achromatic. With the ardour of soul which ever characterizes true genius, he undertakes a pilgrimage to the Royal Observatory of Greenwich, to communicate his discovery to the Astronomer-Royal, in the expectation, doubtless, that the national head of astronomical science would direct all the energies of his mind, and all the powers of his establishment to the immediate discovery of so interesting a star. His errand, however, is fruitless. Mr. Airy was travelling in France, and did not return to his duties at the Observatory till the end of September.†

Report to the Syndicate of the University of Cambridge, p. 3.

In September 1845, previous to this visit to Greenwich, Mr. Earnshaw, of St. Johns, advised Mr. Adams to send an account of his researches to the Philosophical Society of Cambridge; an advice which he, unfortunately, did not follow.

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215

Undisturbed by this disappointment, Mr. Adams proceeds to perfect the elements of his new planet. The results were slightly different from those he communicated to Mr. Challis; but he made the important addition of a list of the residual errors of the mean longitude of Uranus from 1690 to 1840, after taking into account the disturbing influence of the new planet. These errors were very small, with the exception of that of Flamstead's isolated observation in 1690. "This comparison of observation with the theory implied the determination of all the unknown quantities of the problem, both the corrections of the elements of Uranus, and the elements of the disturbing body. The smallness of the residual errors proved that the new theory was adequate to the explanation of the observed anomalies in the motions of Uranus, and that as the error of longitude was corrected for a period of at least 130 years, the error of radius vector was also corrected. As the calculations rested on an assumption, made according to Bode's law, that the mean distance of the disturbing planet was double that of Uranus, without the above-mentioned numerical verification, no proof was given that the problem was solved, or that the elements of the supposed planet were not mere speculative results. The earliest evidence of the COMPLETE SOLUTION of an inverse problem of perturbations is to be dated from October 1845."

This complete solution of the problem, thus justly characterized by Professor Challis, crowned with a Corinthian capital the noble pillar which Mr. Adams has reared for himself in the Temple of Fame. Nothing now remained but to look for the planet. Elated, doubtless, with his triumph, he hastens a second time, on the 21st of October, to the Royal Observatory of Greenwich, to announce his results, and explain his methods, and to induce Mr. Airy to look for the star. The Astronomer-Royal is again absent, and Mr. Adams returns to his College without any prospect of a search for his planet. Fortunately, however, he left at the Observatory a paper containing the results of his investigations, and a complete solution of the problem, as described by Professor Challis. In this paper lie gives the following ele ments of the orbit of the new planet :

Mean distance (assumed nearly in accordance with

Bode's law),

Mean sidereal motion in 365-25 days,

38.4.

1° 30' 9.

The Astronomer-Royal acknowledged the receipt of this im

portant communication on the 5th November; but he neither

congratulates Mr. Adams on the solution of the problem, nor offers, either by himself or his assistants, to look even for the planet. He is still without faith in his science, and he contents himself with merely saying to Mr. Adams that he "should be very glad to know whether this assumed perturbation (namely, that of the new planet), will explain the error in the radius vector of Uranus?" This chilling and unsatisfactory reply to such a communication as that of Mr. Adams is to us utterly inexplicable, and could not fail to sting an ardent mind conscious of its powers, and equally conscious of their triumph. In his own remarks upon this letter, Mr. Airy takes a singular view of it. "I considered," says he, "that the trial whether the error of radius vector would be explained by the same theory which explains the error in longitude, would be truly an experimentum crucis; and I waited with much anxiety for Mr. Adams' answer to my query. Had it been in the affirmative, I should at once have exerted all the influence which I might possess either directly or indirectly, through my friend Professor Challis, to procure the publication of Mr. Adams' theory!" It is not difficult to conjecture why Mr. Adams returned no answer to such a query. He was doubtless chagrined with the apathy with which his discovery was met. His journeys to the Royal Observatory, and his communication to its Director, were fruitless, and the answer to the query which was put to him was virtually answered in Mr. Adams first solution, which Mr. Airy possessed; for, as Professor Challis states, 66 errors of radius vector were as readily deducible from the first solution as from the other." But supposing that Mr. Airy's anxiety had been gratified by the expected communication from Cambridge, what would Mr. Adams have gained by it? Mr. Airy would have used his influence to procure the publication of Mr. Adams' theory. Mr. Adams could have done this himself. It was already sufficiently published by a communication to the two principal Observatories in Great Britain; and all that Mr. Adams wanted was neither Mr. Airy's approbation nor his influence, but simply his assistance, as the Royal Observer, in practically detecting the new planet.

Before proceeding with our narrative, let us pause a little and consider the real state of the problem of a new planet at the epoch at which we have arrived, or of the inverse problem of perturbations, as it has been called, that is, a problem in which, in place of determining the perturbations produced upon any one planet by another, whose orbit and place are given, to determine the orbit and place of an unseen and unknown planet, or to discover such a planet intellectually, by the perturbations which it produces on another planet. On the 30th of October, no mathematician, dead or living, had solved this problem, or was engaged in solving it. Alexis Bouvard had tried it, and might

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have succeeded had he not been told that it was impossible. The illustrious Bessel had resolved to grapple with it, and Mr. Airy, with all the data at his elbow, and with his powerful mind and high intellectual genius, might have anticipated them all, had he withdrawn himself from less legitimate pursuits. Mr. Adams alone had solved it. He communicated his solution to the Director of the Observatory at Cambridge, and to the Director of the Royal Observatory of Greenwich, in order that, as practical astronomers, they might discover the planet whose existence and whose locality he had demonstrated. So anxious was he to give the PUBLIC the benefit of his discovery, (that is, to have the planet seen in the heavens, the only possible benefit in which the public, or even astronomers were concerned,) that he made two journeys to Greenwich to accomplish it. Mr. Adams has, therefore, the sole and undivided merit of being the first discoverer of this remarkable body. No act on his part, and no subsequent researches on the part of others, can affect this great truth. He, and he alone, first solved the problem and pointed to the star. Had he even kept his secret, or embalmed it, according both to French and English custom, in the folds of a sealed packet, intrusted to the private keeping of credible witnesses, or deposited it in the archives of an academical body, his merit as the first discoverer, and the magnitude and interest of the discovery would still have been the same. The only effect of such a secret disposal of his discovery would have been in favour of those who might be engaged in the same research. It would have increased the probability that any second discoverer had not been acquainted with his previous labours. Let us just add to this supposition one equally important, that in October 1845, Professor Challis and Mr. Airy had, one or both, directed their telescope to the 325th parallel of longitude, and seen the planet ;-then we should never have heard more of the claims or even of the labours of others, for at that date no other philosopher had entered upon the research. With what justice then can their negligence, or apathy, or failure, have any influence whatever over the reality and importance of the finished labours of another? As truly might we maintain that the heat and sunshine of to-day have been reduced by the cold and darkness of the morrow, as that the glory of Mr. Adams could be dimmed by the absence of Professor Challis, or the invisibility of Mr. Airy.

Leaving these questions for future discussion, we shall now proceed with our chronological narrative. M. Le Verrier, a young French mathematician of great genius, had distinguished himself by a series of admirable memoirs on the most difficult topics of physical astronomy. His memoirs on the great inequality of Pallas-his new determination of the perturbations of Mercury, and his researches on the rectification of the orbits of comets, had

won for him the favour of the Academy of Sciences, and must speedily have gained for him an European reputation. In the summer of 1845, M. Arago, with his usual ardour for the promotion of science, represented to M. Le Verrier the importance of studying the perturbations of Uranus. A great number of hypotheses, as M. Le Verrier remarks, had been invented to explain them, and it had been doubted whether the motion of this planet was subject to the great principle of universal gravitation. Abandoning the researches on comets which he had undertaken, our author devoted himself to the task suggested by his friend, and on the 10th November, 1845, he communicated to the Academy of Sciences his First Memoir on the Theory of Uranus, which was printed in the Comptes Rendus of the same date, and which, according to the Astronomer-Royal, did not reach England till December. After determining the perturbations produced by Jupiter and Saturn, and correcting the elliptic elements of the planet, he found that there still existed irregularities, which, to use his own words, "might depend on other causes, the influence of which he would appreciate in a second Memoir.' "This Memoir," to use Mr. Airy's words, " placed the Theory of Uranus on a satisfactory foundation;" and such was the estimation in which it was held, that when a vacancy had occurred in the Institute in the Section of Astronomy, by the death of Cassini, M. Le Verrier was, on the 19th Jan. 1846, elected in opposition to M. Edouard Bouvard, by a majority of forty-four to nine votes.

The year 1845 closed, and five months of 1846 passed away before M. Le Verrier produced his Second Memoir, and till the first of June 1846, when that Memoir was published in the Comptes Rendus of that date,† the idea of a new planet, as the certain cause of the irregularities of Uranus, was never once stated or published. His second Memoir, entitled Researches on the Motions of Uranus, contains an able reduction and discussion of all the observations of Uranus, ancient and modern. Le Verrier shows that there is " a formal incompatibility between the observations of Uranus and the hypothesis that that planet is subject only to the action of the Sun and the other planets acting conformably to the principles of universal gravitation ;" and he proceeds to examine the different causes to which this discrepancy has been ascribed. "No sooner" says he, "was it conjectured some years ago, that the motion of Uranus was modified by some unknown cause, than all possible hypotheses were hazarded respecting the nature of that cause. Each, it is true, followed sim