On the New Employment of Artillery, and the Revolution it is destined to produce in the System of Modern Tactics. By Lieut.-General Okounef, of the Russian Army Twenty Days in an Atlantic Steamer. By Brevet-Major Luke Death of Picton. By W. S. Passmore, Brighton Instruction of Officers-Military Messes. By Colonel Firebrace A Romance of the Mediterranean. By W. H. G. Kingston, Esq. 359, 520 STORY OF THE NEW PLANET NEPTUNE. (Concluded from No. 222, page 14.) UNDER this impression we shall, at the most knotty turns of the case, hand in the special test of official documents. Now it appears from the Report of the Astronomical Society for November, 1846, as well as that made by Professor Challis to the Syndicate of Cambridge, on the 12th of December following, that Mr. Adams had long formed the resolution of trying, by calculation, to account for the anomalies in the motion of Uranus: "he showed me," says Mr. Challis, "a memorandum made in 1841, recording his intention of attempting to solve this problem as soon as he had taken his degree of B.A. Accordingly, after graduating in January, 1843, he obtained an approximate solution by supposing the disturbing body to move in a circle at twice the distance of Uranus from the Sun. The result so far satisfied the apparent anomalies in the motion of Uranus, as to induce him to enter upon an exact solution." For this purpose he required a set of reduced observations, and applied to obtain them from Greenwich, through the intervention of Mr. Challis; and this was the first distinct intimation to the AstronomerRoyal: "Cambridge Observatory, Feb. 13, 1844. "A young friend of mine, Mr. Adams, of St. John's College, is working at the theory of Uranus, and is desirous of obtaining errors of the tabular geocentric longitudes of this planet, when near opposition, in the years 1818-1826, with the factors for reducing them to errors of heliocentric longitude. Are your reductions of the planetary observations so far advanced that you could furnish these data? and is the request one which you have any objection to comply with? If Mr. Adams may be favoured in this respect, he is further desirous of knowing, whether in the calculation of the tabular errors any alterations have been made in Bouvard's Tables of Uranus besides that of Jupiter's mass." To this application, Mr. Airy immediately returned this reply: "Royal Observatory, Greenwich, 1844, Feb. 15. "I send all the results of the observations of Uranus made with both instruments (that is, the heliocentric errors of Uranus in longitude and latitude from 1754 to 1830, for all those days on which there were observations, both of right ascension and of polar distance). No alteration is made in Bouvard's Tables of Uranus, except increasing the two equations which depend on Jupiter by part. As constants have been added (in the printed tables) to make the equations positive, and as part of the numbers in the tables has been added, part of the constants has been subtracted from the final results." Dates now begin to be of paramount interest in the story, since a very discreditable rumour obtained, to which we must presently allude, on account of its notoriety. The next letter which appears, shows that Mr. Adams derived advantage from the communication; it is from Mr. Challis to the Astronomer-Royal: "Cambridge Observatory, Sept. 22, 1845. "My friend Mr. Adams (who will probably deliver this note to you) has completed his calculations respecting the perturbation of the orbit of Uranus by a sup* We should here state, that the first clear exhibition of the theory of Uranus was certainly made by the routine operations at the Cambridge Observatory; and the beautiful reductions there tabulated, were eminently useful in all stages of Neptune's discovery. U. S. MAG., No. 223, JUNE, 1847. M posed ulterior planet, and has arrived at results which he would be glad to communicate to you personally, if you could spare him a few moments of your valuable time. His calculations are founded on the observations you were so good as to furnish him with some time ago; and from his character as a mathematician, and his practice in calculation, I should consider the deductions from his premises to be made in a trustworthy manner. If he should not have the good fortune to see you at Greenwich, he hopes to be allowed to write to you on this subject." To this Mr. Airy appends a remark, "On the day on which this letter was dated, I was present at a meeting of the French Institute.” This incidental observation, slight as it is, has raised a bubble in the minds of some of the magnates of the periodical press, and several of their followers. A sturdy assailant took the field in the Mechanics' Magazine, and unprovided with either proof or probability, trumpeted the delinquency of the Astronomer-Royal to the world: how that he, sojourning in Paris, did then and there most imprudently, as well as naughtily, let the cat out of the bag, supplied Le Verrier with Adams's work, and informed the wondering Frenchmen all about the new planet. Yet this Seer cannot have had the slightest basis for so bare-faced an assertion; for from the incontrovertible internal evidence of the Report read to the Astronomical Society, and which we are quoting, the Astronomer-Royal must be acquitted of the silly but foul charge by every pure-minded investigator. On receiving a copy of Le Verrier's Memoir, on the 23rd or 24th of June, of the following year, he thus returned his acknowledgements: "Royal Observatory, Greenwich, 1846, June 26. "I have read, with very great interest, the account of your investigations on the probable place of a planet disturbing the motions of Uranus, which is contained in the Compte Rendu de l'Académie of June 1; and I now beg leave to trouble you with the following question. It appears, from all the later observations of Uranus made at Greenwich (which are most completely reduced in the Greenwich Observations of each year, so as to exhibit the effect of an error either in the tabular heliocentric longitude, or the tabular radius vector), that the tabular radius vector is considerably too small. And I wish to inquire of you whether this would be a consequence of the disturbance produced by an exterior planet, now in the position which you have indicated? "I imagine that it would not be so, because the principal term of the inequality would probably be analogous to the Moon's variation, or would depend on sin 2 (v-v'); and in that case the perturbation in radius vector would have the sign - for the present relative position of the planet and Uranus. But this analogy is worth little, until it is supported by proper symbolical computations." Now here there is not the most distant allusion to Mr. Adams, which must have been the case, had the writer committed himself at Paris, as so deliberately alleged. Most of Adams's friends were staggered by the boldness of his problem, as announced by so young a mathematician: and though he showed that his hypothetical body would satisfy all the anomalies in the most trustworthy observations of Uranus, still, under what they deemed a justifiable scepticism, they lost the moment for victory. Had there been hope and confidence Le Verrier and Adams must have changed places; but while the former was brought out in full daylight, the latter was shrouded in secresy. Though the basis was sound, there was not sufficient faith: so that even this, the first instance of a solution of the abstruse and difficult analytical investigation of the inverse problem of perturbations*, was not made public. It was unfortunate that it appeared to the Plumian Professor as "so novel a thing to undertake observations in reliance upon merely theoretical deductions, and that while much labour was certain, success appeared very doubtful," that he neither engaged in the pursuit himself, nor afforded to others the means of doing so. Under a similar misgiving, the Astronomer-Royal says, that when he found Le Verrier's place for a disturbing planet was the same, to one degree, as that given by Mr. Adams's calculations, which he had perused seven months earlier, he began to look to it. "To this time,' he says, "I had considered that there was still room for doubt of the accuracy of Mr. Adams's investigations; for I think that the results of algebraic and numerical computations, so long and so complicated as those of an inverse problem of perturbations, are liable to many risks of error in the details of the process. I know that there are important numerical errors in the Mécanique Céleste of La Place; in the Théorie de la Lune of Plana; above all, in Bouvard's first Tables of Jupiter and Saturn; and to express it in a word, I have always considered the correctness of a distant mathematical result to be a subject rather of moral than of mathematical evidence. But I now felt no doubt of the accuracy of both calculations, as applied to the perturbation in longitude. I was, however, still desirous, as before, of learning whether the perturbation in radius vector was fully explained." The later remark brings us upon another point in this curious and eventful bit of history. When Mr. Adams made his first statement, Mr. Airy requested to know, "whether the assumed perturbation will explain the error of the radius vector of Uranus?" To this inquiry, from some cause or other unexplained, no immediate answer was returned: but on asking Le Verrier the same question, he received a ready and precise reply, the observed errors of the radius were corrected in his orbit, that they corrected themselves, without any direct consideration; and he added, "Excusez moi, Monsieur, d'insister sur ce point. C'est une suite du désir que j'ai d'obtenir votre suffrage." We can readily allow for the cautious feeling which made the question of the radius vector so strongly insisted upon, as a crucial instance of the actual strength of the supposed discovery, and it might have been answered in some way or other. But this ought not to have been an obstruction, especially as Adams had eliminated all the errors of longitude, which was his principal object; and it seems that he actually employed a method of calculation which required him to compute the co-efficients of the expression for error of radius vector, before computing the co-efficients of the expression for error of longitude. It is, therefore, to be regretted that this co-ordinate should have impeded the Cambridge correspondence, by giving, however unintentionally, the appearance of a slight to the referee. The inverse ratio of perturbations, is that in which the computations may be made from apparently anomalous motions in the body under influence, and not from the known attractions of the body influencing in other words, from known disturbances of a planet in known positions, to find the place of the disturbing body at a given time. Here, as the reason necessarily bears from the effect to the cause, and not from the cause to the effect, for that was unknown, the problem was one of extreme difficulty, and heretofore-as far as we know-untried. The plot was now thickening. At a meeting of the Board of Visitors of the Royal Observatory at Greenwich, the Astronomer-Royal alluded to the impending discovery of a new planet, since there was a singular accordance between the investigations of Adams and Le Verrier. From this remark, and here we speak advisedly, though not in accordance with M. Arago's argument, originated the eloquent expression of Sir John Herschel to the British Association, at Southampton, on the 10th of September. Having observed that the last year had given another new planet (Astrea) to our system, he added," It has done more: it has given us the probable prospect of another. We see it as Columbus saw America from the shores of Spain. Its movements have been felt, trembling along the far-reaching line of our analysis, with a certainty hardly inferior to that of ocular demonstration." And the same discussion led Professor Challis to contemplate a search for the suspected disturber, a search not before thought of. The Astronomer-Royal transmitted to Cambridge suggestions for the examination of a region of the heavens 30° long, in the direction of the ecliptic, and 10° broad, having the theoretical locus of the planet at its centre and at the same time he made a liberal offer of assistance, even at his own cost, the which, to our surprise, was not accepted. A modification of the suggested plan was adopted, and 3,150 positions of stars were recorded; but it so happened that this was like sweeping a large Turkey carpet in quest of a lost diamond, which might have been detected by its inherent brilliance on the spot where it was dropped; and though this course was adopted to prevent ultimate disappointment, yet a careful scrutiny with the powerful telescope employed, must have produced the planet in the early part of August. Mr. Adams had found the mass to be about three times that of Uranus, and had thence inferred that the brightness would not be below that of a star of the 9th magnitude; but his consequent request that the planet might be sought for by its physical aspect, was neglected. This is matter of regret, since, from the surpassing interest of the question, it ought to have been fished for nine months before, namely, in October, 1845, when both the prediction and the detection would infallibly, and without competition, have fallen to Cambridge; and England would have enjoyed an incontestable right to a sort of astronomical feat which, great as she is, she is most in want of. These are the elements upon which the scrutiny was eventually conducted: Such being the conditions of the case, we must proceed to consider them, and we trust at least to bring impartiality to bear. According to the Astronomer-Royal's incontestable evidence, no doubt can be entertained of Adams's being de facto the first to predict the existence and locus of a new planet. Such a body was à priori probable; and the skilful geometer showed, by giving all the possible elements (node and inclination out of the question), and the place at a given time,— |