THE General Chronicle, AND LITERARY MAGAZINE. SIR FOR NOVEMBER, 1811. To the EDITOR of the GENERAL CHRONICLE. IR,-Having continued to observe the Comet with various instruments on every favourable occasion since the first day of September, I selected, from upwards of thirty observations, five which could be confided in as very nearly accurate. The days of the observations were the 1st, 8th, 15th, 23d, and 30th, of September. From these five, reduced to longitudes and latitudes, it was conceived that the elements of the orbit might be pretty correctly determined according to the celebrated formula in the Méchanique Céleste of La Place. The task of observing, continued frequently through the greater part of the night, as well as the labour of reducing and comparing the observations, made me gladly avail myself of the co-operation of Mr. Cross, my Mathematical associate in the Andersonian Institution. It is to this gentleman's familiarity with the transcendental calculus, and eminent facility of computation, that I am enabled, at the interval of above a month after our first view of the comet, to announce the elements of its orbit being ascertained. All that the first five observations, however accurate, can possibly give, is the approximated values of the quantities. I believe, however, that the following numbers will be found little removed from the truth, and whatever inaccuracy may exist will be corrected by subsequent observations. Perihelion distance, or nearest approaching of the Comet to the Sun, 94 millions 724 thousand 260 miles; time of its perihelion passage, Sept. 9. Comet's distance from the earth, September 15, 142 millions 300,000 miles. Comet's distance from the sun on the 15th, 95 millions 258,840 miles. Distance of the earth from the sun at that time, 95 millions 505,932 miles. Length of the tail, SS millions of miles. CEN. CHRON. VOL. III. NO. XIII. R 3 Motion Motion of the comet retrograde, or its real motion from east to west, being the reverse of what it appears to be at present to a spectator on the earth. The real size of the comet, as deduced from its appearance in the grand Herschelian telescope, is about that of our moon. The brilliant central nucleus is invisible even in the ten feet Herschelian, and in every smaller instrument. The three other elements, besides the Perihelion distance and time of the passage through this point, are neither interesting nor intelligible to the general reader. We shall take an early opportunity of laying them before the world, accompanied by the whole series of observations made on the comet at this establishment. For illustrating in a popular manner, the real motion of the comet, Mr. Cross is preparing a solid figure, by which its actual path, together with that of the earth, will be accurately represented. The orbit of this comet differs entirely from that of 1661; nor does there seem, in any one of the 98 comets whose orbits are calculated and recorded, sufficient resemblance to establish identity between them. I am, sir, your obedient servant, Glasgow Observatory, Oct. 3. ANDW. URE. To the EDITOR of the GENERAL CHRONICLE. SIR,-I hope the following facts relative to the comet will not be unacceptable to your readers. Since my communication to you of the 4th, relative to the comet, announcing the determination of the elements of its orbit made at this Establishment, I am happy to perceive, in the London papers which arrived to-day, the result of Burckhardt's second approximation. The talents of this gentleman as a computer are well known, and highly appreciated by the learned world. Between his time of the perihelion passage and ours, there is a difference of no more than three days, and the whole periodof the comet's revolution, I am satisfied, exceeds considerably one hundred years. It is to be remarked too, that Burckhardt never ventured to give to the public his first trials, and therefore, whatever differences exist between his numbers and ours may have been obtained at his second calculation. The inaccuracy of the first he expressly admits in his letter to the Editor of the Moniteur, which begins in the following manner: Having been requested to correct my first determination,' &c. I wish it to be understood, however, that the appearance of his statement has not shaken, in the least degree, the confidence I humbly conceive due to our own results. The observations from which these are derived were performed with with the instruments of Troughton; instruments unquestionably superior to any other in the world. But we have still more direct assurance of the accuracy of our observations, by comparing them to the numbers which have been published from the highest authority (the astronomer-royal) in the Philosophical Magazine of this month. The longitudes of the comet, determined at Greenwich and Glasgow Observatories, coincide to the fraction of a minute. The time of the perihelion passage may be considered as pretty accurately fixed, either for September 12 or 9, or as is more probable, at some intermediate period.-From this we can fully explain some of the phenomena generally remarked. From the 9th, as stated in the Glasgow papers, by a Correspondent, the comet was observed to increase considerably both in brilliancy and in the apparent magnitude of the coma, but particularly of the tail, in the course of eight days. This verifies very happily the observation of Sir Isaac Newton, that it is not till immediately after the perihelion passage, comets acquire their maximum of lustre and of size. The enlargement therefore uniformly takes place at that time, whether the comet is coming nearer us, or moving in the opposite direction. The quantity of increase due to its approximation alone, in six or eight days, can be calculated, and we know that there is no instrument in Scotland capable of measuring the change of apparent magnitude produced by this cause. Whether the exquisite micrometer of Troughton, applied to our great Herscheliau telescope, may show any diffe rence, I shall be able to ascertain in a few days, as that instrument is lately dispatched from London for us. I must acknowledge, however, that I entertain very slender hopes of success in this kind of observation on a minute body surrounded with such a nebulosity, and at a distance from us much greater than that of the sun. It has been said, that this comet was ascertained to be the same with that of 1661. The two are as different as can be imagined in every respect; hence we may see how much safer, in the event, scientific investigation is than vague conjectures. I subjoin the elements of the comet of 1661, and those now given by Burckhardt. SIRA To the EDITOR of the GENERAL CHRONICLE. IR,-As few are disposed or are competent to enter into long and tedious astronomical computations, perhaps the following extracts from a series of calculations which I have lately made on this Comet, may not prove uninteresting to some of your readers. The comet was in its ascending node on the 11th of July, at a distance of 138,117,270 miles from the sun, its motion is retrograde, and its orbit passes close (within 39 minutes) to the north pole of the heavens; it was nearest the sun on the 18th of September, and to the earth on the 11th of October, when its distance from the latter body was 113,630,450 miles. On the 22d the Comet will be equi-distant from the earth and sun, and in about three days after, its distance from the earth will begin to increase very rapidly, and therefore we must expect its brilliancy, its apparent size, and length of tail, to diminish in a similar ratio, after that time, though I think it will be visible till about the end of December; but, before then, it will cease to become an object of public attention. Had this Comet made its appearance about five months earlier, the position of the earth would have been such, as to have rendered their minimum distance from each other much less than at present, and, instead of a tail of 12 degrees, it would have appeared to extend over more than 30 degrees of the heavens; its nearest distance from the earth would have been no more than 44,405,850 miles, and its apparent diameter would have been increased nearly in the inverse ratio of its distance. This Comet is certainly much larger than the moon, but it is difficult to measure its diameter, owing to the dense atmosphere that surrounds it, yet, from its distance, and the apparent size of its nucleus, it must be a body of considerable magnitude: its tail is not less than 49,401,900 miles in length. I might have given the computed geocentric longitudes and latitudes along with the dis tances above, but as its apparent course (which is direct) is not that of a great circle of the sphere, it would be difficult to lay its track on a celestial globe with any degree of accuracy; and, moreover, its present geocentric track lies in a comparatively blank part of the heavens. The The telescopic appearance of this Comet is said to be different from that of any other. From my own observations with Dolland's acrometer, I see nothing in the appearance of the coma but what may be easily accounted for by the principles of projection. Your's respectfully, Epping, Oct. 16. T. S. To the EDITOR of the GENERAL CHRONICLE. IR,-The science of astronomy discovers to us such an inconceivable number of suns, systems, and worlds, dispersed through boundless space, that if our sun, with all the planets, moons, and comets, belonging to it, were annihilated, they would be no more missed, by an eye that could take in the whole creation, than a grain of sand from the sea-shore;-the space which they occupy is comparatively so small, that it would scarcely be a sensible blank in the universe, although the Georgium Sidus, the outermost of our planets, revolves about the sun in an orbit of 10,830 millions of miles in circumference, and some of our comets make excursions upwards of 70,000 millions of miles beyond the orbit of the Georgium Sidus. At that amazing distance, they are incomparably nearer to the sun than to any of the fixed stars, as is evident from their keeping clear of the attracting power of all the stars, and returning periodically by virtue of the sun's attraction. The stars, then, being at such immense distances from the sun, cannot possibly receive from him so strong a light as they seem to have, nor any brightness sufficient to render them visible to us; for the sun's rays must be so scattered and dissipated, before they reach such remote objects, that they can never be transmitted back to our eyes, so as to render those objects visible by reflection. The stars, therefore, shine with their own native and unborrowed lustre, as the sun does; and since each particular star, as well as the sun, is confined to a particular portion of space, never changing its situation with regard to another as the planets do, it is evident that the stars are of the same nature with the sun. Whoever imagines that they were created only to give a faint glimmering light to the inhabitants of this globe, must have a very superficial knowledge of astronomy, especially as there are many stars which are not visible without the assistance of a good telescope, and therefore, instead of giving light to this world, can only be seen by a few astronomers. This, moreover, were to entertain a mean opinion indeed, of the divine wisdom; since, by an infinitely less exertion of |