94' COSMOS. 



the immeasurable regions of ethereal space ; but they must be 

 regarded as isolated occurrences, exercising no more general 

 or alterative effects on cosmical relations than the breaking 

 forth or extinction of a volcano within the limited sphere of 

 our Earth. 



A third interior comet, having likewise a short period of 

 revolution, was discovered by Faye, on the 22nd of Novem- 

 ber, 1843, at the Observatory at Paris. Its elliptic path, 

 which approaches much more nearly to a circle than that of 

 any other known comet, is included within the orbits of Mars 

 and Saturn. This comet, therefore, which, according to 

 Goldschmidt, passes beyond the orbit of Jupiter, is one of 

 the few whose perihelia are beyond Mars. Its period of 

 revolution is 7-^ years, and it is not improbable that the 

 form of its present orbit may be owing to its great approxi- 

 mation to Jupiter at the close of the year 1839. 



If we consider the comets in their inclosed elliptic orbits 

 as members of our solar system, and with respect to the 

 length of their major axes, the amount of their eccentricity, 

 and their periods of revolution, we shall probably find that 

 the three planetary comets of Encke, Biela, and Faye, are 

 most nearly approached in these respects, first, by the comet 

 discovered in 1766 by Messier, and which is regarded by 

 Clausen as identical with the third comet of 1819 ; and next, 

 by the fourth comet of the last-mentioned year, discovered by 

 Blaupain, but considered by Clausen as identical with that of 

 the year 1743, and whose orbit appears, like that of Lexell's 

 comet, to have suffered great variations from the proximity 

 and attraction of Jupiter. The two last-named comets would 

 likewise seem to have a period of revolution not exceeding 

 five or six years, and their aphelia are in the vicinity of 

 Jupiter's orbit. Amongst the comets that have a period of 

 revolution of from seventy to seventy-six years, the first in 

 point of importance with respect to theoretical and physical 

 astronomy is Halley's comet, whose last appearance, in 1835, 

 was much less brilliant than was to be expected from preced- 

 ing ones ; next we would notice Gibers' comet, discovered on 

 the 6th of March, 1815 ; and lastly, the comet discovered by 

 Pons in the year 1812, and whose elliptic orbit has been 

 determined by Encke. The two latter comets were invisible 

 to the naked eye. We now know with certainty of nine 



