320 EXPERIMENTS RELATIVE TO METEORITES. 



those of iron; the disappearance of a part of their elements may have brought on 

 a total disintegration. 



THIRD SUB-GROUP, OR CRTPTOSIDKROUS METEORITES. 



In the meteorites of which wo form the third suh-gronp, the iron is scanty, and 

 Us grains are so fine as to have passed unperceived until M. Gustave Rose demon- 

 strated their presence. The name of cryptosiderous (z/ju-roc, hidden,) expresses 

 Uiis character. This sub-group constitutes, in fact, a transition from meteorites 

 containing metallic iron to meteorites destitute of it ; it has thus been considered 

 until the present time as pertaining to the 'after. 



But it is chiefly by the composition of the stony part that these meteorites 

 differ from the preceding, that is to say, from the common or oligosiderous type. 

 The principal section to be distinguished in the cryptosiderous series is that of 

 the aluminous meteorites. It is characteriy.ed, in a mineralogical point of view, 

 by a mixture of two distinct minerals, win di often occur, however, in a state of 

 confused crystallization, namely, aiigitc pyroxene and anorthite feldspar. In 

 addition, magnetic pyrites or pyrrhotine is also found, often forming hexagonal 

 crystals perfectly distinct, as was long sin( e observed by M. Gustave Hose.* 

 The aluminous meteorites referred to this i'.ection have recently received from 

 that eminent mineralogist tlie name of cu\rites, from suxpcroc, distinct. The 

 alumina and lime occur here in larger proportion tlian in meteorites of the com- 

 mon t3'pe, while on the contrary the magnet.ium is in less quantity. t It will be 

 seen that this composition presents a certain analogy with some well-ivuown 

 lavas, such as those of Etna, formed of pyroxene associated with labradorite 

 feldspar ; while it approximates still more closely to the composition of other 

 lavas with anorthite, which have been met with at the Thjorsa, in Iceland. 



In the aluminous meteorites, the external coating is lustrous instead of being 

 dull, as in meteorites of the connnon type ; it is at the same time remarkable fV)r 

 the distinctness of the striae and indurated globules which it presents. This two- 

 fold circumstance appears to correspond to a greater fusibility of the substance, 

 due to the simultaneous presence of the aliujiina and lime. Besides the meteor- 

 ite of Juvinas, may be cited, as pertaining to this type, those which fell 22d 

 May, 1808, at Stannern, in ]\Ioravia, and 13th June, 1819, at Jonzac (Charente- 

 inferieure). The presence in one of these meteorites, examined in 1825 by M. 

 G. Rose, of minerals having the same crystalline forms with those of terrestrial 

 mineral species, which have moreover the same composition, constitutes an im- 

 portant fact in the study of these cosmic bodies ; for it serves to show the unity 

 of the laws which govern the inorganic world throughout the immensity of space. 



A sec(nid section comprises meteorites principally formed of magnesian sili- 

 cates. It is represented by the meteorite which fell 3d October, 1815, at Chas- 

 siguy (Ilaute-Marne). The magnesian silicate is peridot, which we have men- 

 tioned as existing in preceding groups, and which presents itself here, constitut- 



* See, respecting ihe crystallized minerals which occur iu meteoric stones, " Annates de 

 Chirnie ct de Fhysiqiic," 1826. 



tAs an example, we will cite the meteorite which fell KJth June, 1821, at Juvinas, 

 (Ardecljc, ) the analysis of which, made heretofore by Vauguelin and by Laugier, has been 

 lately repeated by M. Kammelsberg. According to the latter, the composition is as follows : 



Pyroxene augite 62.65 



Feldspar anorthite 34.56 



Apatite 0.60 



Titauite 0.25 



Chrome iron 1.35 



Magnetic oxidulated iron 1.17 



Magnetic pyrites '. 025 



Total 100.83 



