280 METEORS AND AEROLITES. 



opinion derived its chief authority from Dr. Izarn's Lithologie 

 Atmospherique ; a book of merit as an historical record, but 

 largely imaginative in all that relates to these metallic and 

 earthy vapours ' massees spheriquement, et isolees les unes 

 des autres ' which he presumed to exist in the atmosphere 

 around us. 



We speak of this theory in the past tense, because, though 

 at first taken up by many, it was impossible long to maintain 

 it in the absence of all proof, and in the face of facts which 

 gave it every character of physical impossibility. Vauquelin, 

 to whom Izarn addressed his views, explicitly repelled them : 

 ' J'aime encore mieux croire que ces pierres viennent de la 

 lune, que d'admettre que les substances les plus fixes que 

 nous connaissons se trouvent en assez grande quantite dans 

 1'atmosphere pour y produire des concretions aussi conside- 

 rables que celles qu'on dit en etre tombees.' We hardly 

 indeed need comment on the infinite improbability that such 

 materials as iron, nickel, silex, magnesia, &c., should be 

 absorbed into and exist in the atmosphere ; exist, too, in its 

 upper and lighter stratum, since the most refined analysis 

 has detected no such elements in the lower. Not less im- 

 probable is it that matters diffused with such exquisite 

 minuteness, as these hypothetically must be, should thus 

 suddenly coalesce into a dense solid. The action of cen- 

 tripetal aggregation must be carried on simultaneously over 

 a vast extent of space to produce such effect ; nor, in truth, 

 do we yet know any physical force or law capable of the 

 peculiar action required. A more positive objection to the 

 atmospheric theory is the direction of movement and fall, as 

 repeatedly ascertained in the case of these bodies. Had they 

 been formed in the atmosphere, whatever the process of 

 aggregation, their fall must have been perpendicular to 

 the earth's surface at the place, instead of oblique, as we 

 generally find it to be. 



