small glasses, till January, or perhaps. later; and lastly, that the distance from the comet to the earth would be always considerably greater than that from the earth to the sun. These predictions, which have been confirmed by the event, created no sensation at the time, because they came too soon. M. OLBERS, a distinguished philosopher, particularly in the astronomy of comets, having been deputed by the town of Bremen, to attend the baptism of the King of Rome, carried from Paris and circulated through Germany, the elements calculated by M. Burckhardt; and M. GERGONE, of Nismes, made use of them to construct an ephemeris of the course of the comet, from February 1811, to the end of March 1812. This work, which was at first interesting, because the comet last year attracted every body's attention, was afterwards useful, as it enabled us to find its position when obliged to employ glasses. Astronomers, however, after having specified so long beforehand whatever they thought would interest the public, continued to observe the comet in silence, and to compare their observations, in order to rectify the trivial, though inevitable, errors which always appear in the first sketch of an orbit. M. de Flaugergues, who first saw the comet, noted down all his observations: after having determined the elements of the orbit, he thought he saw some resemblance between them and those of a comet which was seen in China, about 510 years ago. This remark, if it could be verified, would give the real measure of the revolution and the ellipsis of the comet; but such knowledge is in its nature very uncertain, inasmuch as it can only be obtained from the observations made on one course of appearance of a heavenly body. M. de Flaugergues, however, by searching into the records of antiquity, found that there had been several comets, all of whose appearances were different, in the course of 510 years; and they would give to his conjecture a high degree of probability, if the indications of historians were not too vague to allow of a calculation of the respective orbits: hence we can have no certain knowledge on this head. Messrs. BOUVARD, GAUSS, and LINDENAU, who also determined the orbit of the grand comet of 1811, thought, on the contrary, that its period could not be less than from 1000 to 1500 years, and that' it might even be much longer This comet, however, which has made so much noise, had nothing to render it more interesting thau any other. After having ascertained the course which it would take, the astronomers could do no more than repeat the proceedings which are printed in every treatise on astronomy. But this was not what in terested the great mass of the public, They seemed to want dissertations on the physical constitution of the comet; on the nature and cause of the long tail, that appeared like a veil over a lady's face, symmetrically disposed on each side, in two opposite curves, at first at a tolerable distance, but which afterwards came together, and finally incorporated. On this subject astronomers are certainly no better informed at present than they were in the last century. The explanation given by NEWTON, of the tails of comets, is satisfactory, on the whole, as to the most remarkable phenomena; that is, as far as relates to the direction which is always, or almost always, taken, in the prolongation of the line which joins the centres of the sun and the comets, with a slight curva ture inclining towards the place that the comet has just quitted. But it is diffi cult to account for the inclination of the other branch in a contrary direction, a phenomenon which has been remarked by all astronomers. Why does this tail, or the atmosphere of which the tail is the cause, or prolongation, appear to be separated completely from the head or nucleus? This obscure interval which was constantly observed, does not appear with all comets; but it is not, on the other hand, without example. Is the separation real; or is it an optical illusion? But, if it really do take place, by what is it caused? These are the questions which geometricians and astronomers cannot answer, because they cannot offer satisfactory explanations, and they will not listen to or give any others. While wanting these desirable solutions, men seek, in foreign journals, for accounts which are presented as novel or curious. Some writers have told us how many miles the comet travelled in a certain time. Vain inquiry, which an astrono mer may sometimes make, out of complaisance, but to which he does not attach the smallest importance. The comet at the time of its greatest motion, did not equal that of Venus, still less that of Mercury. We can see Venus aimost always: she approaches much nearer to the earth than the comet has has ever done; but nobody has thought The second comet was discovered at Marseilles, on the 16th of November, by M. PoNs, who had already found out seven or eight others. The Director of the Imperial Observatory in that town, M. BLANPAIN, informed us of the fact, and transmitted the remarks he had made on it, on the 17th, 18th, and 19th, of the same month. Its right ascension was about ten minutes per day, opposite to the order of the signs, and its declination towards the north pole, thirtythree minutes. It was then very weak, and could scarcely be seen at Paris; while the bad weather obstructed the efforts of our astronomers, and they found much difficulty in making a few doubtful observations. Nevertheless M. Burckhardt calculated its orbit, though he only considered it as a shapeless outline; but it was found to be nearly the same as that which M. GAUSS had ascertained by other observations, made, perhaps, under rather more favourable circumstances, on account of the more southern latitude of his residence. The comet, however, passed its perihelion soon afterwards, and shortly disappeared. Its least distance from the sun was 8" of the distance of the earth from the sun. Notwithstanding this distance, which accounts for its feeble light and the slowness of its motion, if the weather had been finer it would have been better seen than the beautiful comet which preceded it; because its nucleus was more apparent and more perfect. We know, on the whole, that it did not resemble any of the numerous comets whose orbits have been defined. NEW LUNAR TABLES. The calculation of the two orbits just mentioned, notwithstanding the difficulties of the process, was only an amusement for M. Burckhardt,- -a sort of recreation, which did not prevent him from putting the finishing touches to the profound researches which he had engaged in concerning the motions of the It is only six years since the Institute and the Board of Longitude moon. 3 loaded, with unqualified praise, the Tables of M. BÜRG, astronomer, of Vienna. These tables, constructed from many thousands of excellent observations, supported besides by the analytical researches of COUNT LAPLACE, and augmented by several new equations, have been generally adopted by astronomers, and nothing has hitherto cast the slightest suspicion on that confidence which a minute examination bad ensured to them. Thus, the first idea of M. Burckhardt was not exactly to construct new tables, but some which would be of a more convenient form for calculators. MAYER had remarked, that he could diminish considerably the number of equations and arguments, by employing only the real place of the sun, and by materially abridging and correcting the theories, by the equations already calculated. This form of the tables, by Mayer, had so many inconveniences, that M. SCHULZE, of Berlin, was induced to remodel them, in order to make them still more brief and clear. M. CARLINI, of Milan, also, very lately announced, that he had conceived a project for making a similar alteration in the tables of Bürg. M. Burckhardt, however, had anticipated him in this idea; and on this occasion he wished to satisfy himself whether there were not already extant some other equations which deserved insertion in the lunar tables. In other times, when an astronomer attempted to form tables of a planet, he began them entirely anew, and ran the risk of performing much less than his predecessors. By the method, however, which is now adopted, a man no longer exposes himself to the chance of retrograding: he finds out what corrections have been made in those tables which are most esteemed, and he compares these with his own observations. Thus he at once introduces the latest corrections which have already been in. serted, and unites them to other efficient but neglected equations. Such is the plan pursued by M. Burckhardt. ile has begun by giving to the Tables of M. Burg a new arrangement; and, on comparing them under this form, not only with all the calculations of the last-mentioned philosopher, but also wich many more recent observations, he has found in this laborious task many anvans tages: amongst these we may mention of submitting to a new analysis the ce ficients so ably discussed by A. 3K2 in order to draw from them direct observations, and to introduce the new equations, which the observations required to be done with clearness; and, at the same time, not to lengthen the calculations; since, on the one hand, if he increased the number of equations, on the other, he simplified the arguments, which is an inestimable advantage, particularly to the calculators of ephemerides. On finishing this work M. Burckhardt submitted his tables to a new proof, by comparing them with all the passages of the moon at the meridian, which could be observed in the first ten months of 1811, either by himself, at the Observatory of the Military School, or by M. Bouvard, at the Imperial Observa tory. Nothing more can yet be said about these tables, which have only just been submitted to professional inspection; but there is every reason to believe that they will be found as accurate, and certainly more convenient, than those of M. Bürg, published by the Board of Longitude at Paris, and this is enough to induce astronomers to wish for their speedy publication, NEW TELESCOPE. About the same time that M. Burck. hardt was employed on his Lunar Tables, M. ROCHON Constructed a new Telescope, the object-glass of which is made of Ice land Spath. It has two foci, equi-dis tant from each other, 50 that it produces the effect of two glasses of different lengths, by enabling the observer to see at the same time an object at a great dis tance, and one which is very near. This curious instrument has made much noise amongst the philosophers of France; so much so, that the Chevalier DELAMBRE, one of the learned editors of the Magazin Encyclopedique, declines offering any opinion on the subject; although a long dissertation on the invention has appeared in the Moniteur. M. Rochon presented this telescope to the National In stitute on the 1st of April, 1811; he stated, that it would serve to measure horizontal refractions; and he requested that Messrs. MALUS and ARAGO (of whose optical discoveries we shall shortly give an account in the Monthly Magazine), might be employed to verify his experi ments. His idea is considered to be very ingenious; but experience only can shew of what use it may be in astronomy. 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THE next Supplement to the Monthly The first meeting of the Royal Society this season, touk place on the 5th of November, when a communication from SIR HUMPHREY DAVY to the President, was read. It contained an account of a new and very extraordinary detonating substance, which Sir Humphrey formed by the action of chlorine on ammonia, and which he regards as a compound of chlorine and azote. It appears in the form of a yellow oil, it freezes by cold, and becomes elastic by heat, and explodes most violently, either by gentle heat or by friction: it seems to be by far the most powerful detonating compound known. Sir Humphrey, in operating on a particle not bigger than a grain of mustard seed, was severely wounded in the eye by the explosion. We are, how ever, able to state that he is recovering, and that no permanent danger, it is hoped, will result from the accident. It has been supposed, on the authority of a private letter, that a similar substance has been discovered in France, but that the preparation of it has been con cealed with a view of applying it to the purposes of war. ARCHDEACON COXE will publish, on the 20th of the present month, Memoirs of the Kings of Spain of the House of Bourbon, from the Accession of Philip the Fifth to the Death of Charles the Third, 1700-1788, with an Introduction relative to the Government and State of Spain. It will be drawn from original Documents and secret Papers, many of which have never been published, and form three volumes quarto. A work on the grounds of Protestantism; or the causes which contributed to the secession of our forefathers from the errors and corruptions of the Church of Rome; by the late Dr. ROBERTSON, will appear this winter. The REV. ROBERT WALPOLE is preparing for publication, Memoirs on Earo pean and Asiatic Turkey, from the manuscript journals of some modern It will travellers in those countries. It has recently been discovered that iron, at a red heat, may be sawed, with a common saw, in the manner of wood. In this way a block of iron may be sawed into iron planks for numerous purposes. At a white heat it is found to clog the saw. Mr. W. EARLE meditates the early publication of a new Monthly Review, |