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The poor Carthaginian rubbed his eyes, as he took up one letter after another from the heap before him ; but his dreams seemed still upon him. “ Not a letter can I see,” he exclaimed, as he again rubbed his eyes, and snuffed his candle.“ Friend, lend me your eyes, or you may just take the whole load away with you.”
I am none of the best at deciphering handwriting,” replied the driver. “Why then I must call my wife, for she is as sharp as a needle.” The wife was called, and, in gown and cap, soon made her appearance ; the candle and the papers placed in the middle, wife, husband, and driver set about deciphering the hieroglyphics; but that the wife had the character of being as sharp as a needle, I should have augured ill of the labours of this triumvirate. Whether right or wrong, however, the selection was soon made, and the budget once again committed to the wagon.'
pp. 167, 168.
ART. III.-1. Eine merkwürdige astronomische Entdeckung
und Beobachtungen des Kometen vom Jul. 1819, vom Herrn Doct. Olbers in Bremen.-A remarkable astronomical discovery, and observations of the comet of July 1819, by Dr Olbers of Bremen. Published in Bode’s Astronomisches
Jahrbuch for 1822. 1. Ueber einen merkwürdigen Kometen, der wahrscheinlich bei
dreijähriger Umlaufzeit schon zum viertenmale bei seiner Rückkehr zur Sonne beobachtet ist, vom Herrn Prof. J. H. Encke, Adjuncten der Sternwarte Seeberg bei Gotha.On a remarkable comet which has probably a periodical revolution of about three years, and which has been four times observed in its descent towards the sun. By Professor Encke, assistant in the observatory at Seeberg, near Gotha. Pub
lished in the same work. 3. Ueber die Bahn des Ponschen Kometen, nebst Berechnung
seines Laufs bei seiner nächsten Wiederkehr im Jahr 1822, vom Herrn Prof. Encke, Direktor der Herzogl. Sternwarte Seeberg bei Gotha.—On the orbit of Pons' (or rather Encke's] comet, with the computation of its apparent path about the time of its next appearance in 1822, by Professor Encke, director of the Ducal observatory at Seeberg, near Gotha. Published in the Astronomisches Jahrbuch for 1823.
It is well known that the orbits of most of the comets are extremely eccentric, and approach so much to the form of a
parabola, that it is usual to compute the elements of the orbit upon the supposition that they move in this curve ; and it is found in general that the observations made on those bodies are well represented by this hypothesis, which leaves however the time of the revolution wholly indeterminate. In fact, there are but very few comets, in which any considerable ellipticity of the motion has been perceived, and only two instances in which the periodical revolution has been determined to any great degree of accuracy, namely, Halley's comet, which
appeared for the fifth time in 1759, according to his prediction, with a periodical revolution of seventy five years; and Olbers' comet, which was observed for the first time in 1815, with such very evident marks of an elliptical motion, that its periodical revolution could thence be ascertained to a considerable degree of accuracy, and it was found, by a careful examination of all the observations, to be nearly of the same length as that of Halley’s comet ; though in other respects, the two orbits are very different from each other.
We have now to add to the list another comet, still more remarkable, on account of the shortness of its revolution, which is only one thousand two hundred and five days. It had been observed in 1786, 1795, and 1805; but the defects of the observations in 1786 and 1795 had prevented its identity from being noticed, until its appearance in 1819, when its elliptical motion was discovered by Professor Encke. The details and calculations relative to this remarkable discovery are given in the papers mentioned at the beginning of this article.
The first of these papers contains extracts from letters of Di Olbers, in which he communicates his observations on the great comet, visible by the naked eye in Europe and in this country, in July 1819; together with his calculations of the parabolic elements of its orbit, which agree very nearly with those made and published in this country. He also mentions, with great brevity, his discovery of the identity of the comet of 1786 and 1795, with the small for Encke's] comet of 1819.
The second paper contains a full account of the calculations of Professor Encke, to determine the orbit of this comet. He, very modestly, names it Pons' comet, from the circumstance that Mr Pons first discovered it, both in 1805 and in 1819; but Professor Bode prefers to call it Encke's comet, after the name of the discoverer of the true orbit, in like manner as was done in the case of Halley and Olbers; and it is highly probable that this last name will be adopted by astronomers.
When this comet was discovered at Marseilles by M. Pons, on the 26th of November 1819, it was in the neck of the constellation Pegasus. It appeared tolerably bright, and a nucleus was several times perceived, but no appearance of a tail. It was not observed in Germany till December 22, 1818, and eontinued visible till January 12, 1819, describing in its course an apparent arch of about twenty three degrees.
In calculating the parabolic orbit of this comet, Professor Encke used only the German observations. After various trials he found that he could not obtain any parabola that would represent them within three minutes, and the error was much greater in the early observations made at Marseilles, being above thirty minutes in right ascension, and six minutes in declination; a şure indication that the orbit varied much from a parabola, and that it was necessary to notice its elliptical form.
After some preliminary calculations, Prof. Encke assumed the following elliptical elements of the orbit in 1819, using always the mean time for the meridian of Seeberg, and the mean equinox for the year in which the comet was observed.
d. Time of passing the perihelion 1819 Jan. 27.275 Longitude of the perihelion
1570 5' 53" Longitude of the ascending node
334 43 37 Inclination of the orbit to the ecliptic
13 38 42 Eccentricity (comet's dist. from sun=1) 0.849 Mean distance from the sun
2.2131 Periodical revolution, about 1203 days. Motion direct.
These elements represent the place of the comet, during its appearance, to a great degree of accuracy. For, out of forty two observations of the right ascension and declination, thirty five are given to less than half a minute, and no error exceeds 1' 33": so that there can be no doubt that the true figure of the orbit in 1819 is very nearly given by the above elements.
When this result had been obtained, it became an interesting object of inquiry to find whether the comet had been before observed by astronomers. Upon looking over the general table of the orbits, Professor Encke selected the first comet of 1805 (marked 107 in Delambre's table) as a former appearance, with an interval of four revolutions. It was near the constellation Ursa Major, when first discovered by Mr Pons, Oct.
20, 1805, and appeared as a star of the fourth magnitude, with a nucleus and a very faint tail, 24° in length. It continued visible the 15th of November. The parabolic orbit had been computed by several persons, with considerable difference in the results, which had been imputed, in great measure, to the incompleteness of the observations. In these different calculations the time of passing the perihelion varied from November 17th to 18th; place of the perihelion 147° to 149°; of the node 340° 10 345°; inclination 15 to 171°; perihelion distance 0.346 to 0.379. The parabolic elements, published by the accurate and indefatigable Professor Bessel," (Monatliche Correspendenz, b. xiii. xiv.) did not represent the right ascensions and declinations without errors of 26', 11', 8', 7', 6', &c. Instead of which, Professor Encke found that the following elliptical orbit would satisfy all the observations made in 1805.
d. Time of passing the perihelion 1805, Nov. 21.529. Longitude of the perihelion
156°47' 24" Longitude of the ascending node
334 20 10 Inclination of the orbit
13 33 30 Eccentricity
0.8461 Mean distance from the sun
2.2131 In fifty observations of the right ascension and declination, thirty two are given, by these elements, to less than half a minute, and the greatest error is 1' 39".
The near agreement of these elements with those of the comet of 1819 made Professor Encke feel confident that it was the same comet. This discovery having been communicated to Dr Olbers, led him to a farther investigation of the subject, and he, with his usual sagacity and promptness, immediately perceived and gave the information to Professor Bode, that it had also appeared in 1786 and in 1795.
During its appearance in 1795, it was about three minutes in diameter, not well defined, without any tail or nucleus, and was first discovered near the constellation Cygnus. It was found extremely difficult to make the observations at that time correspond with a parabolic orbit, and the results of different astronomers were very discordant; making the time of passing the perihelion December 14th or 15th ; longitude of the perihelion 157° to 171°; the node 353° to 361°; inclination 10° to 24°; perihelion distance 0.212 to 0.258. After a new reduction and computation of the observations, Professor
Encke found that the following elliptical elements would represent very well the observations made at that time.
Time of passing the perihelion 1795, Dec. 21.47. Longitude of the perihelion
156°41' 20" Longitude of the ascending node
334 39 22 Inclination of the orbit
13 42 30 Eccentricity
0.8489 Mean distance from the sun
2.2131 In 1795 the comet was frequently observed in a part of the heavens where there were no bright stars, favourably situated to compare with it, and, on this account, the observations of different astronomers sometimes varied considerably from each other. However, out of thirty eight observations of the right ascension and declination, twenty three were within one minute, and but very few of the observed places varied more than two minutes from the calculations.
On the 17th and 19th of July 1786, this comet was observed in the constellation Aquarius by Messrs Messier and Mechain. These two observations are not sufficient to determine the elements, three being the least number that can possibly be used. No notice is therefore taken of it in Delambre's table. It appears however from the above elements of Encke's comet, that it must have been near the perihelion about the 31st of January 1786, and the calculations of Professor Encke confirm those of Dr Olbers, proving that the following elements will satisfy these two observations.
d. Time of passing the perihelion 1786, Jan. 30.88 Longitude of the perihelion
156°38' Longitude of the ascending node
334 08 Inclination of the orbit
13 36 Eccentricity
0.848 Mean distance
2.208 It may be observed that other elements may be found, which will also satisfy these two observations, but as these elements vary but little from those found for Encke's comet in 1795, 1805 and 1819, there can be no doubt that it was the same.
To compare these results together, we must allow for the precession of the equinoxes during the intervals of the successive appearances. Reducing them all therefore to the mean equinox of 1806, the elements deduced from the observations of the four different appearances of the comet will be respectively,