MAY BECOME SATELLITES TO THE EARTH. 



patible with dynamical laws. If its particles have inertia they 

 must necessarily stand, with respect to the sun, in the relation 

 of separate and independent minute planets, each having its 

 own orbit, place of motion, and periodic time. The total mass 

 being almost nothing compared with that of the sun, mutual 

 perturbations are impossible, though collisions between such as 

 may cross each other's paths, may operate in the course of 

 indefinite ages to effect a subsidence of at least some fraction 

 of it into the body of the sun or those of the planets.* 



25. There are certain supposable circumstances under which 

 the earth might pass near to one of these masses, the conse- 

 quence of which would be that it would become a satellite of 

 the earth, and would accompany it as the moon does in its course 

 round the sun, and would, if it were large enough, be visible 

 by reflected light like the moon. But since, so far as is yet 

 known, these bodies are far too small to be seen thus at any 

 distance, at which they could possibly revolve without being 

 speedily arrested by the resistance of the atmosphere, and 

 brought down to the surface by terrestrial gravitation, it follows 

 that the earth may actually be attended by hundreds of such 

 invisible moons. Sir J. Herschel is even of opinion that these 

 not only exist, but that some of them may be so large, and of 

 such texture and solidity, as to shine by reflected light, and 

 become visible (such at least as are very near to the earth) for 

 a brief moment, suffering extinction by plunging into the 

 earth's shadow, in other words undergoing total eclipse.t Sir 

 John Lubbock is of opinion that such is the case, and has sup- 

 plied rules and mathematical formulae for calculating their 

 distances from observations of this kind.tjl 



26. M. Petit, Director of the Observatory of Toulouse, has 

 made observations and calculations of this kind, which induces 

 him to conclude that there is at least one meteoric stone of con- 

 siderable magnitude, which is attached as a satellite to the 

 earth. Its orbit is at about 5,000 miles from the surface, and 

 therefore 9,000 miles from the centre, or about twenty-six times 

 nearer than the moon. It makes a complete revolution in three 

 hours and twenty minutes, and therefore revolves round the 

 earth about seven times per day. 



27. In enumerating the hypotheses which have been proposed 

 to explain the phenomena of aerolites, we have omitted to notice 

 one, which, if for no other reason, may be regarded as entitled 

 at least to be mentioned on account of its antiquity. As the 



Herschel's Astron., p. 616. f Ibid., p. 521. 



+ Phil. Mag., 1848, p. 80. 



Comptes rendus, Acad. Sc., Oct. 12th, 1846, and Aug. 9th, 1847. 



159 



