THE ASTEROIDS. ' 235 



mineral from being extensively employed as a source of commercial borax. 

 —J". Arthur Phillips, F. G-. S., m Popular Science Review. 



ASTRONOMY. 



THE ASTEROIDS. 



Every now and then the papers announce the discovery of a new planet. 

 The occurrence indeed has become so frequent of late as to attract very 

 little notice except from professed astronomers, and they, to speak the 

 truth, are none too cordial in their welcome of the little strangers thus ad- 

 ded from time to time to the already embarrassingly large family under 

 their charge. For while these new planets are quite as troublesome to 

 provide with ephemerides and orbits as their larger sisters, they are ex- 

 tremely insignificant as regards their importance in the econoniy of the 

 solar system, being seldom more than forty or fifty miles in diameter and, 

 as individuals, entirely without sensible influence upon the motions of 

 other heavenly bodies. We say as individuals, because they belong to a 

 numerous group known as the Asteroids (so called because they look like 

 little stars), and the united attraction of the whole family does jDrodhce 

 upon the orbit of Mars a perfectly sensible, though vevj minute effect, from 

 which Leverrier has computed that the combined mass of the whole flock 

 would suffice to make up a globe not exceeding one-third the size of the 

 earth, and probably a good deal smaller. 



At present the number of these bodies known is 172: the whole number 

 existing is probably to be reckoned by thousands, since it would take more 

 than five hundred of the largest of them to make up the mass named. 



Ceres, the first of them, was discovered on the first day of the nineteenth 

 century, that is, January 1, 1801. 



It had been noticed nearly two hundred years before, by Kepler, that 

 the progression in the numbers representing the distances of the planets 

 from the sun is such as to suggest the existence of an invisible body in the 

 space between Mars and Jupiter, and he at one time went so far as to pre- 

 dict its discovery. He abandoned the idea, however, supposing that in his 

 celebrated but fantastic theory of the polyedrons he had found the key to 

 the mysteries of the planetary system. Titius, in 1772, revived the original 

 suggestion, and gave to the law of distances nearly the same form as that 

 in which it was stated a few years later by Bode. 



In 1781 Uranus was discovered at a distance from the sun so closely 

 corresponding with the law as to satisfy astronomers that it could be no 



