MARS ASTEROIDS JUPITER SATURN URANUS. 



93 



frightful explosion would ensue. Lagrange, in an ingenious memoir, determined that an 

 explosive force not greater than twenty times that of a cannon-ball would have sufficed to 

 detach the asteroids from a primitive planet, and convert them into independent bodies 

 describing ellipses similar to their actual orbits ; and a force equal to this is often exerted 

 by our volcanoes. Some however, rejecting the idea of any assimilation between a planet 

 and the boiler of a steam engine, have had recourse to concussion from a cometary shock to 

 account for the supposed rupture. The strong atmospheric developments of Ceres and 

 Pallas are upon this surmise explained to be portions of the gaseous envelope of the 

 comet's nucleus, the nebulosity called the hair, which distributed itself among the several 

 fragments caused by the percussion, and formed an immense atmosphere around them. 

 But the fact of Vesta exhibiting no certain traces of an atmosphere is against this 

 theory, as well as that of the extreme tenuity of cometary bodies rendering it unlikely 

 that any such tremendous physical change would transpire upon collision. It is difficult 

 to assign the event conjectured to have taken place to any cause which shall" be free 

 from strong objections, but still, the more thoughtfully the elements of the asteroids are 

 considered, the more probable the presumption will be deemed, that they once composed 

 a single body, which has been shattered by some potential agency. In addition to the 

 intimations of this occurrence already stated, it is significant of the great convulsion, that 

 the bodies themselves appear not to be round like the other planets. Sir David Brewster, 

 after recapitulating their phenomena, remarks, that they concur to prove, with an evi- 

 dence amounting almost to demonstration, that the four bodies have diverged from one 

 common node, and have therefore composed a single planet. If such a disruption has 

 happened, the supposition is next to certain that the asteroids are not the only extant 

 memorials of it, but that other remains exist, of various extent, which may elucidate the 

 often witnessed and singularly mysterious occurrence of meteoric showers. 



JUPITER, the next in succession after the telescopic planets, is the noblest member of 

 the solar family in his dimensions, and the brightest in his appearance with the exception 

 of Venus, whom, however, he rivals in splendour, although more than seven times her 

 distance from the sun. His mean distance from the central body is 495 millions of miles. 

 His entire path in space extends over about 3000 millions of miles, an orbit accomplished 

 in nearly twelve years, at a mean rate of twenty-nine thousand miles an hour. Jupiter 

 travels over 4' 59" of the zodiac in a day, somewhat less than one-twelfth of a degree, or 

 30 20' 32" in a year, rather more than a sign. His course in the heavens may therefore 

 be very easily traced. In whatever constellation he is seen on a certain night, a year 

 hence he will be seen equally advanced in the next constellation, and two years afterwards 

 in the next. For twelve years to come, he will, at a mean rate, pass through the signs 

 of the zodiac as follows : 



1845. Pisces. 



1846. Aries. 



1847. Taurus. 



1848. Gemini. 



1849. Cancer. 



1850. Leo. 



1851. Virgo. 



1852. Libra. 



1853. Scorpio. 



1 854. Sagittarius. 



1855. Capricornus. 



1856. Aquarius. 



Jupiter occupies but 9 h 55 m 49 s in his axical rotation. Thus, in the time in which we 

 have one day and night, he has two, each about five hours long, the sun by day, and the 

 stars by night, with his own moons, apparently flying across his heavens more than twice 

 as fast as the celestial bodies appear to traverse ours. By this rapid spinning upon his 

 axis, his equatorial inhabitants will be carried round at the rate of 26,000 miles an hour, 

 which is farther than the equatorial inhabitants of the earth are carried by its diurnal 

 motion in twenty-four times that period. Of the stately dimensions of this fine planet, 

 some idea may be formed from the statement, that a chain extending from the earth to 

 the moon would not compass his equatorial circumference ; and that, supposing a sailing 



