THE PLANETS, AEE THEY INHABITED 1 



such striking analogies to the earth, another group consisting of 

 six or seven-and-twenty bodies, circulate round the sun, as 

 represented in the plan of the system given in this tract, Chap. 

 II., fig. 1. The number of these is augmented every year by the 

 discovery of some which were not before seen. 



22. These bodies, which have been called PLANETOIDS or 

 ASTEROIDS, obey the law of gravitation in their motion round 

 the sun. Their distances from that luminary are not only 

 different one from another, but they differ from all the other 

 planets in their extremely small magnitude. In the telescope 

 they are seen as stars of the tenth or twelfth magnitude, and 

 their real magnitudes are so minute that they have never yet 

 been certainly ascertained, notwithstanding the number and 

 power of the telescopes that have been directed to them. 



As to their origin, and the parts they play in the economy of 

 creation, nothing can be offered but the most vague and uncertain 

 conjecture. According to the opinion of some, they are the 

 minute fragments of a single planet, which has been smashed to 

 pieces by collision with the solid nucleus of a comet, assuming 

 the possible existence of such a body. According to others, the 

 fracture may have been produced by internal explosion, arising 

 from causes similar to those which produce earthquakes and 

 volcanic phenomena. Others again reject altogether the hypo- 

 thesis of the fracture of a formerly existing planet, and substitute 

 for it the contrary hypothesis, that these numerous minute 

 bodies are the germs or constituent elements of a future planet, 

 which will be formed by these bodies gradually coalescing into 

 one globe, some of them, perhaps, assuming the character of 

 satellites to it. 



These are speculations which, however ingenious and attractive, 

 are beside our present purpose. It is plain that the planetoids, 

 as they now actually exist, present none of the analogies to the 

 earth which are so conspicuous in the other planets. 



