340 



Mr. R. P. Greg on Meteorolites or Aerolites, 



by a force capable of overcoming the mutual attraction of its 

 particles, and the mass of matter so broken would inevitably be 

 disperaed in every direction, and in parts of various sizes. 



" The impulses given by the explosion would gradually dimi- 

 nish, and the parts, in gravitating towards the sun, would be- 

 come influenced by progression and rotation. To this view there 

 does not appear to be any demonstrable objection. It was sug- 

 gested that under such a disruption the form of the orbits 

 assumed by the fragments, and their inclination to the ecliptic, 

 or to the orbit of the original planet, would depend upon the size 

 of the fragments, or the weight of their respective masses : the 

 largei' mass would deviate least from the original path, while the 

 smaller fragments being thrown off with greater velocity , will re- 

 volve in orbits more excentric and more inclined to the ecliptic. 

 Now that is precisely what happens. Ceres and Vesta are found 

 to be the largest of the asteroids, and their orbits have nearly 

 the same inclination as some of the old planets ; while the orbits 

 of the smaller ones, Juno and Pallas, are inclined to the ecliptic 

 13° and 34°*5 respectively. Lagrange computed the force of 

 explosion necessary to burst a. planet, and convert a portion of it 

 into a systematic wanderer. By the process described in the 

 Connaissance des Tems for 1814, he arrived at the conclusion, that 

 were a fragment to be impelled with a velocity equal to 121 

 times that of a cannon-ball, it would become a direct comet, but 

 a retrograde one if the velocity were 156 times. With weaker 

 impulse, however, the fragment would describe an ellipse, and 

 thus, it is presumed, the asteroids probably were impelled with 

 only twenty times that velocity. The exact circumstances of 

 these extraordinary bodies are not yet sufficiently determined, 

 and the correction of future observations is urgently necessary ; 

 but the following table, constructed from details in the Nautical 

 Almanac for 1845, exhibits a very close approximation to their 

 principal elements. The planets are arranged in their order of 

 distance from the sun, and in the semi-axes of their orbits ; the 

 semi-axis of the earth's orbit is taken as unity. 



" Such are the extraordinary conditions of the asteroids, whose 

 intersecting orbits, leading them almost within hail of each other, 

 80 to speak, at the rate of more than 40,000 miles an hour, may 



