EXPERIMENTS RELATIVE TO METEORITES. 321 



m^ nearly the whole of the mass. It is identical with that which oconid on 

 the earth, and contains disseminated grains of chrome iron.* On the stone of 

 Chassigny, as on other meteorites, there is a crust resulting from a superticial 

 fusion. 



IV. METEOKITES OF TIlK FOURTH GROUP* OR ASIDEROUS. 



The meteorites in which no iron disseminated in a metallic state can be recog- 

 nized are rare, and the more attentively meteorites are ."tiidied with a view to 

 the presence of metallic iron, the more is the number of the specimens of this 

 last group reduced ; it is nearly restricted at present to Ihc carbonaceous meteor- 

 ites. These ])resent in their composition peculiarities of such a kind that it 

 woidd have been in)possible to believe in their origin, had not their fall been 

 witnessed. A recent occasion has allowed these interesting bodies to be studied 

 with minute attention. It is the presence of carbon which characterizes them, 

 not free or in the state of graphite, as in certain ferruginous meteorites, but in 

 adniitted combination with hydrogen and oxygen ; it is also the presence of 

 combined water ; finally, it is the i)resence of soluble, and even deliquescent 

 saline constituents. To complete these distinctive characters, it must be added 

 that a double carbonate of magnesium and iron, of the species hreimcritc, has 

 been met with in the meteorite of Orgueil. 



In certain respects carbonaceous meteorites ally themselves with those of 

 which we have already spoken. Like the latter, they contain magnesian sili- 

 cates, including sometimes oxides of nickel, cobalt, and chnmie. There is i'oiuid 

 also oxide of magnetic iron, magnetic pyrites, innumerable microscopic crys- 

 tals, having scarcely a diameter of 1.30 of a millimetre,t and linally chrome iron. 



The presence of carbon, in a state of hydro-oxygenated combination, and 

 analogous to the results of vegetable decomposition, has led to an investigation 

 whether the carbonaceous meteorites might not contain remains which had 

 belotiged to living beings. But the most delicate researches have disclosed 

 nothing of' this kind. However this may be, the presence of substances easily 

 volatilized, or alterable under the action of heat, would prove that at the moment 

 when the carbonaceous meteorites penetrated into the atmosphere they were cold. 

 The incandescence which they have undergcjne has produced, by the fusion of 

 their superticial portion, a thin crust, but the Aveak conductibility of the con- 

 Btituent matter has preserved the internal parts from sensible alteration. 



The carbonaceous meteorites, of which we possess specimens, are referable to 

 four descents, all quite recent. The lirst took place at Alais, (Gard,) in 1803 ; 

 the second at the Caj)e of Gt>od Hope, in 1838; the third at Kaba, in Hungary, 

 in 18.57; and the fourth at Orgueil (Tarn-et-Garonne,) in 18G4. We owe to 

 Berzclius, Faraday, and JM. Woehhu-, the discovery of the principal facts relating 

 to the constitution of the meteorites of this sub-group. More recently M. Clofiz 



* Tbb i'ollowiug is the result of the analysis which M. Damour has inado of this iuteresting 

 meteorite : 



Silica ;?:^.30 



Magnesium :? 1 .7R 



Protoxide of iron ~<).7(J 



Protoxide of luangauese I'- 15 



Oxide of chioine l'~-"> 



Potassium t'.<'<j 



Chrome iron and pyroxene -i-^^ 



Total i>y."t) 



This composition is that of the variety of peridot, rich iu protoxide of iron, and kuown inider 

 Xhc \M\\i\ii o'i litjaloaidcriU. (Cinnptrs Ji<7iilus, t. Iviii, IcUl.) 



t Especially iu the meteorites of Orgueil. Comptts Utiulus, t. Iviii, May 30, ldG4. 



21 S 



