118 COSMOS. 



of iron, from the aerolites of Siena, in which the Iron scarcely 

 amounts to 2 per cent., or the earthy aerolite of Alais (in the 

 Department du Gard), which broke up in water ; or lastly, 

 from those of Jonzac and Juvenas, which contained no metallic 

 iron, but presented a mixture of oryctognostically distinct 

 crystalline components ! These differences have led mine- 

 ralogists to separate these cosmical masses into two classes, 

 namely, those containing nickelliferous meteoric iron, and 

 those consisting of fine or coarsely-granular meteoric dust. 

 The crust or rind of aerolites is peculiarly characteristic of 

 these bodies, being only a few tenths of a line in thickness, 

 often glossy and pitch-like, and occasionally veined.* There 

 is only one instance on record, as far as I am aware (the 

 aerolite of Chantonnay, in La Vendee), in which the rikd was 

 absent, and this meteor, like that of Juvenas, presented like- 

 wise the peculiarity of having pores and vesicular cavities. 

 In all other cases the black crust is divided from the inner 

 light-gray mass by as sharply-defined a line of separation as 

 is the black leaden-coloured investment of the white granite 

 blocks f which I brought from the cataracts of the Orinoco, 

 and which are also associated with many other cataracts, as, 

 for instance, those of the Nile and of the Congo River. The 

 greatest heat employed in our porcelain ovens would be in- 

 sufficient to produce anything similar to the crust of meteoric 

 stones, whose interior remains wholly unchanged. Here and 

 there, facts have been observed which would seem to indicate 

 a fusion together ot the meteoric fragments ; but in general, 

 the character of the aggregate mass, the absence of com- 

 pression by the fall, and the inconsiderable degree of heat 

 possessed by these bodies when they reach the earth, are all 

 opposed to the hypothesis of the interior being in a state of 

 fusion during their short passage from the boundary of the 

 atmosphere to our Earth. 



The chemical elements of which these meteoric masses 

 consist, and on which Berzelius has thrown so much light, 

 are the same as those distributed throughout the earth's 



* The peculiar colour of their crust was observed even as early as in 

 the time of Pliny (ii. 56 and 58) : "colore adusto." The phrase " lateribui 

 pluisse," seems also to refer to the burnt outer surface of aerolites, 



f Humb.. Rd. Hist., t. ii. chap. xx. pp. 299-302. 



