332 EXPERIMEXTS RELATIVE TO METEORITES. 



eue and anorthite. Now water, in the presence of wliicU tliese last were formed, 

 conld have been no stranger to their crj^stallization. In no case do these rocha 

 crvstaUize under the conditions of dry fusion, as the niagnesian silicates so read- 

 ily do; fusion transforms them into vitreous and amorphous masses. Hence, the 

 nieteorites of this last type seem rather pi-oducts 1)}' tlie mixed way, which we 

 might imitate, perhaps, by operating in water overcharged with heat. 



As to the carl)onac.eous meteorites, they differ from all others, in that, doubt- 

 less, several of the substances which constitute them have V>ecn formed at a tem- 

 perature but little elevated. At first view, we miglit be tempted to consider 

 them as planetary vegetable earth ; but it is possible, and the supposition is even 

 probable, that these carburetted compounds have been formed without the con- 

 currence of life and represent the last terms of certain reactions. 



§ 3. DEDUCTION'S AS KESPECTS THE FORMATION OF THE TERKESTRIAL 

 GLOBE. — ANALOGIES AND DIFFERENCES BETWEEN METEORITES AND 

 TERRESTRIAL ROCKS. 



We have seen above how much analogy of composition exists between mete- 

 orites and sundry terrestrial rocks. Not only do they include the same simple 

 bodies, but the tliree bodies which predominate in the series of meteorites, namely, 

 the iron, silicium, and oxygen, are also those which predominate in our globe ; 

 besides, we discover therein mineral species common to both and associated in 

 the same manner. 



It should here be remarked that the rocks which offer such traits of resemblance 

 with the meteorites all pertain to the deep regions of the globe. They are 

 eruptive masses of a basic nature, or lavas, or jieridotic rocks, the reseivoir of 

 ■which is situated below the granitic stratum. We will recall (1) the lava formed 

 of anorthite and of pyroxene, and such as has been found at the Thjorsa, in 

 Iceland, for its approximation to the aluminous type (or that of Juvinas), the 

 sixth of the seven principal types of meteorites which have been established 

 above ; (2) the peridot and the Iherzolite, which present striking resemblances 

 with the silicated part of the magnesian meteorites, and particularly with those 

 of the common type. We know, from the examination made of it by M. Damour,* 

 that the Iherzolite is composed of peridot, with which are united enstatite, pyrox- 

 ene, and sometimes spinelle, (picotite). The magnesian meteorites may also be 

 compared to the hypersthene, pervaded by grains of peridot, which has been 

 brought from Labrador. 



But by the side of these resemblances between meteorites and certain terrestrial 

 Classes there exist differences which deserve no less to fix our attention. These 

 differences l)ear essentially on the state of oxidation of the iron. Meteorites, 

 like terrestrial rocks, contain protoxide of iron combined with silicium (silicate) 

 a,nd with the oxide of chrome, (chroniated iron). On the contrary, oxydulated 

 U'on, so frequent in our basic silicated rocks, fails, in general, in the meteorites. 

 (t is there replaced, in some sort, by native iron, which, on the other hand, is 

 ^'anting in our rocks. t 



There is a second difference of the same character with the preceding. The 



* Bulletin de la Socie(S siologique de France, 2d sene, t. xix, p. 413. Ou this occasion, it 

 's mere justice to ackno\vied«:e the acuteness of observation of M. Lolievre, who us early as 

 1767, in anuouucing t.!ie discovery of this remarkable rock, already recognized it as a 

 variety of chrysoHte, or peridot, (Journal de Physique, May, 17(^7, letter to de la Metherie.) 

 Twenty-five years later, M. de Charpeutier supposed he had demonstrated this same rock to 

 be no other than a pyroxene in mass, and this conclusion was hastily and very generally 

 idopted. The variations presented by Iherzolite serve to explain the too absolute couclusiou 

 «f a mineralogist so experienced. 



t It is true that oxydulated iron is found in the carbonaceous meteorites, such as that of 

 Orgueil ; but these last pertain to a rare and wholly special category. 



