METEOES AND AEROLITES. 303 



pour forth periodical showers, but each with an independent 

 orbit of its own ? What physical causes can have produced 

 such separate accumulation or consolidation of these portions 

 of matter ? Both analogy and the known laws of the me- 

 chanism of the heavens, furnish a certain explanation of zones 

 or rings, but we have no similar aid to our understanding of 

 these insulated masses moving in space. Are they residual 

 merely upon the consolidation of larger bodies ? or must we 

 regard them as detached by some unknown force from bodies 

 already consolidated ? The fragmentary character of aerolites 

 as well as the materials composing them, might suggest the 

 latter idea, and the numerous group of excentric planetoids 

 between Mars and Jupiter give sanction to it ; but we have 

 already followed out the argument derived from these 

 sources, and seen how much is wanting to its certainty and 

 completion, 



Before closing this article we must make more particular 

 mention of the valuable work of M. Saigey, recording, in 

 sequel to an Historical Introduction, those long series of 

 observations by M. Coulvier-Gravier, in which latterly the 

 writer himself took an important share. We prefer such 

 separate notice, both because these researches are little 

 known in this country, and because their purport will be 

 better understood from the relation already given of the 

 previous state of knowledge and opinion on the subject. We 

 must begin by stating that M. Saigey acquiesces only very 

 partially in the conclusions we have described as adopted by 

 the most eminent scientific men of the age. He contends 

 that these conclusions are premature ; based in many points 

 on doubtful or insufficient observations ; and pressed forward 

 by astronomers relying too much on analogies drawn from 

 their own more certain science. He asserts that longer 

 research into facts is needful to any theory on the subject; 



