METEOES AND AEROLITES. 287 



it is easy to conceive that the progressive motion of the 

 earth may bring it into such proximity to the numerous and 

 excentric orbits of these meteorites or asteroids, that they 

 become submitted to its influence, and deflected more or less 

 from their course, as we know comets to be by the vicinity of 

 planets ; some actually impinging upon the earth in the 

 form already described ; others merely luminous through 

 certain arcs of their orbits. The number of such orbitual 

 interferences or collisions indicated, as the theory presumes, 

 by luminous globes, shooting-stars, and aerolites may startle 

 some as an objection. But astronomy everywhere deals in 

 numbers which surpass all common comprehension, yet are 

 justified so frequently by certitude of proof, that we cannot 

 refuse belief in others where the evidence is still incomplete. 

 Arago, following one of Kepler's bold anticipations, has 

 calculated that there may be eight millions of Comets having 

 their revolution within the solar system. Meteorites, ac- 

 cording to the present view, approach nearest to the cha- 

 racter and condition of comets. The orbits of the matter 

 thus revolving, (whether it be dense or infinitely attenuated) 

 are probably not less excentric in outline, and have the same 

 vast interplanetary spaces open to them. Numbers, then, need 

 not perplex us here ; and especially if admitting a view we 

 shall notice hereafter, as to the seeming periodicity of the 

 great showers of shooting-stars. 



This cosmical theory of meteors in general has un- 

 doubtedly been gaining ground of late years, while other 

 hypotheses have been stationary or retrograde. It has de- 

 rived argument and illustration from the whole course of 

 physical research during this period ; with the effect of giving 

 a new aspect to the phenomena, and associating them together 

 as parts of a larger system and more general laws. We have 

 placed a volume of the Cosmos of Humboldt among the works 

 at the head of this article, because no philosopher has been 



