Page images
[ocr errors]

1786 1795 1805 1819 Time of Perihel. Jan. 30.88 Dec. 21.47 Nov.21.53 Jan.27.27 Long. of Perihel. 156

55 156 50 156 47 156 55 Do. Ascend. Node 334 25

334 481 334 20 334 33 Inclination

13 36 13 42 13 33 13 39 Eccentricity

0.848 0.849 0.846 0.849 Mean distance 2.208 2.213 2.213 2.213

These elements agree remarkably well with each other, especially when we take into consideration that the disturbing forces of the planets have been wholly neglected in making the calculations. Three revolutions of the comet have been completed in each of the intervals between 1786, 1795 and 1805 ; and four revolutions between 1805 and 1819. Hence it follows that the periodical revolution is about one thousand two hundred and five days, which is rather less than that of the newly discovered planets. In the perihelion it passes within the orbit of Mercury, and at the aphelion is about mid-way between the orbits of these small planets and that of Jupiter.

From these elements it would follow that if the comet pass the perihelion between the months of October and February, it would appear, upon its approach towards the earth, so much to the north of the ecliptic, as to render it visible in our northern climates. But, if it should happen at an opposite season of the year, it would not, in general, be visible, except in places south of the equator; unfortunately, this will in some measure be the case at its next appearance in May 1822.

To determine with precision the time and place when the comet will next appear, would require a complete caloulation of the disturbing forces of all the planets upon the comet from the year 1795 to 1822. The methods of doing this (though much abridged and simplified from what they were, when Clairaut and his associates, with immense labour, calculated the return of Halley's comet) are yet extremely laborious ; and the difficulty in the present instance may sometimes be very much increased, from the circumstance that the comet may pass very near to Mercury, and the attraction of this planet might be so much augmented by its proximity, that its disturbing force, notwithstanding the smallness of its mass, might exceed that of Jupiter, the greatest planet in the system.

The calculations made by Professor Encke, to ascertain nearly the effect of the disturbing forces of the planet upon the

comet, are given in the third of the papers mentioned at the beginning of this article. It is unnecessary to go into any particular detail relative to this subject. We shall merely observe, that the result of his inquiries leaves an uncertainty of about one day in the time of passing the perihelion. He has therefore used two sets of elements, in computing the places of the comet. The first set, which he supposes to be the most accurate, is as follows: counting the mean time from the meridian of Seeberg, and the longitudes from the mean equinox of May 24, 1822.

d. h. Time of passing the perihelion, 1822, May 24, 0. Log. of the mean distance

0.34722 Long. of the perihelion

157° 12' 7" Long. of the ascending node

334 23 24 Inclination of the orbit to the ecliptic 13 20 36 Eccentricity

0.84472 In the second set, the time of passing the perihelion is May 25d. Oh.; the log. of the mean distance 0.34746; the rest of the elements are not altered.

Professor Encke has calculated, in both these hypotheses, the places of the comet, at intervals of four and of two days, from Feb. 25, 1822, to July 27. From this table we have made the following extracts.

Log. dist.


[ocr errors]
[ocr errors]
[ocr errors]
[ocr errors]

Right Ascens. Declination.
1 set. 2 set.
1 set. 2 set.

from O from 1822. Feb. 25 0 44 0 401 7 19 N. 7 16 N.10.2180.391

Mar. 1 2 28 2 24|| 8 4 8 1 0.204|0.386
April 2 19 51 19 38|15 14 15 9 0.0610,3231

May 4 49 41| 49 0||23 36 23 31 9.7830.193 Perih. May 24 81 12 80 33||23 0 123 27 9.5380.019 June 11 91 471 91 5018 18 19 2 9.607 9.902

19 109 59110 53 1 43 S. 1 S.9.855 9.607 July 1134 48 134 51 30 11 26 34 9.966|9.4401 27|234 55|232 6147 2

46 35

0.1249.713 It appears, from this table, that at the time of sunset at Seeberg, in the latitude of 50° 56' N. the comet on the 25th Feb. 1822, will be 261° above the horizon of that place ; March 13th it will be 20°; March 29th, 141°; and April

14th, 11°. Therefore, after the middle of March, it can be observed only in the evening twilight, and, on account of its great distance, it will not have a quarter part the brightness it had when first discovered in 1819, so that it may not be seen in Europe or in the United States ; because after the perihelion, when it approaches the nearest to the earth, it will be too far to the south. It is however strongly recommended to search for it with good night glasses, particularly as it was observed in January 1819, in the evening twilight, only 5° above the horizon. After the perihelion, in southern climates, it will be visible by the naked eye, and from the 24th of May to the 27th of July, its brightness (independent of the effect of the twilight) will be much greater than it was when discovered by Mr Pons in 1819; and it is hoped that its apparent path will be carefully traced at the new observatory at the Cape of Good Hope, as also at Port Jackson, and at other places in the southern hemisphere.

While the astronomers of Europe are thus making, almost every year, important discoveries, which will render the present age forever memorable in the history of science; it is rather a mortifying consideration, that, in America, nothing can be done to assist in the laudable work; since there is not a well furnished observatory on the whole continent, from Canada to Cape Horn; and while Great Britain alone can boast of more than thirty public and private observatories of considerable note, we have not in the whole United States one that deserves the name. It is moreover a subject of regret that the general government, instead of holding out inducements to individuals to procure from abroad the accurate and expensive instruments, necessary for nice astronomical observations (and which can only be made by the delicate hand of a Troughton or a Reichenbach) should virtually impose a fine of several hundred dollars, under the name of duties, upon the person who imports them; and this penalty must be further increased, if he should wish also to procure the voluminous transactions of the Royal Societies of London, Paris, Petersburg, and Berlin, with other similar works, where the treasures of the science of astronomy are to be found. This oppressive tax upon the literature and science of our country, or (as it has been very justly terined on the floor of Congress) this bounty upon ignorance, seems not to comport with the nature of our government, which is founded upon the principle that

New Series, No.9. 5

the people are virtuous and intelligent; and it would therefore seem to be the dictate of a wise policy to encourage, in every possible manner, the means of instruction; with the full persuasion that it is upon the general diffusion of knowledge among the citizens that the safety of our excellent institutions of government must depend.

Art. IV.-A description of the Island of St Michael, com

prising an account of its geological structure; with some remarks on the other Azores or Western Islands. Originally communicated to the Linnean Society of New England. By John W. Webster, M. D. Cor. Sec. L. S. N. E. 8vo. pp. 243. Boston, 1821. The discovery of the Azores forms a very important link in the chain of events, which led to the discovery of the Western World. It was a reward in hand to the enterprise and courage,

which had ventured so far on the broad expanse of the Atlantic, and an earnest of the immortal honor which awaited the bold adventurer, who should follow its waves still nearer to the setting sun. The various objects, which the winds drove on shore upon these islands, afforded so many indications of other land at no great distance to the west, that several navigators were induced to set sail from them in quest of discoveries in that direction, even as early as forty years before Columbus' first voyage. These attempts, it is well known, were unsuccessful; they serve however to show what were the opinions and expectations upon the subject at that day. Ferdinand Columbus, in his account of his father's life and exploits, mentions these circumstances among the motives which induced the great discoverer to sail westward in search of land, and the same are repeated by Herrera, Munoz, Robertson, and Bossi. Whatever may be said of a western passage to India, as the ultimate object of which he was in pursuit, there cannot now be a doubt that his immediate one was that which he first attained, and it is probable that he represented the other as the most important, because he knew it would be so regarded by those whose aid he sought, and also most likely to gain credit. It is not however in this connexion only that the discovery of these islands is an interesting and important event; it was the first considerable

maritime enterprise in modern times; the first movings of that adventurous, exploring, commercial spirit, which has since so fully developed itself, and formed the great characteristic distinction between the present and former ages of the world. We should have been pleased, therefore, if our author had thought this part of his subject deserving of a more particular and fuller notice than he has given it, and we have proofs enough throughout his work, that he could have cleared it of the obscurity in which he finds it involved, if he had made the attempt.

The authority upon which we think most reliance should be placed is that of the globe of Martin Behaim. It is one of the earliest accessible records of the event, and was made by a man well versed in all good learning, especially in geography, who was an inhabitant for some years of one of the islands in question, and the son-in-law of Huerter, the planter of the Flemish colony in Fayal. This globe, as appears by an inscription upon it, was made at the request of the sage and venerable magistrates of the noble and imperial city of Nuremberg according to the discoveries and directions of the chevalier Martin Behaim, learned in the art of cosmography, having himself sailed one third round the world." And it was left by the said Martin Behaim in 1492 to the city of Nuremberg as a testimony of his remembrance and respect, when he was about to leave it, and return to his wise, who dwelt on an island seven hundred German miles distant.' The eastern continent is delineated upon it in conformity to the descriptions of Ptolemy, Pliny, Strabo, and the other ancient geographers, with such additions and corrections as he was enabled to make from the information furnished by Marco Polo and Mandeville, and the islands on the coast of Africa and the Azores from his own and other modern discoveries. Written descriptions of many of these places are given on the globe itself

. We quote that which relates to the question under consideration, from Murr, who, in his life of Behaim, has furnished a most minute and faithful account of the subject of his biography, accompanied with an engraving of the globe, and copies of all the geographical and historical memoranda upon it. In the year 1431, says Behaim, 'two vessels with provisions for two years were sent out to discover the countries beyond St James of Finisterre ; which vessels sailed about five hundred German miles toward the west, and finally discovered there ten islands and landed on them, where they found

« ՆախորդըՇարունակել »