334 EXPERIMENTS RELATIVE TO METEORITES 



on the surface of the earth, is, beyond doubt* predominant at a certain depth. 

 Hence, its importance may be infeired as well in regard to our globe as to the 

 rest of our planetary system, as far, at least, as we can judge of the latter l)y the 

 specimens which reach us. The rocks of peridot, therefore, excluded until now 

 from the general classifications of lithology, would seem destined to hold here- 

 after a special and considerable place in them. By annexing serpentine to the 

 rocks in qirestion we might comprise theui under the name of i\\Q peridot ic f am ily, 

 or that of cosmknl rocks. 



Tliere is, in the mean time, no room for surprise that peridot does not come in 

 greater abundance to the surface of the globe. It is, in effect, the most basic 

 silicate that is known, and it has a strong tendency to take up silicium and to 

 become transformed into a more acid silicate, such as enstatite or pj-roxene, as is 

 shown by the experiments lieretofoi'e detailed. Now, to cume from its primitive 

 seat to the surface, it must necessarily have traversed rocks more acid than itself, 

 and having kilometers of thickness. On these it would inevitably react, and 

 may thus have given rise to those pyroxenic or amphibolic rocks which are so 

 numerous, and which establish a sort of transition between pure peridot and 

 pyroxene. Perhaps it is to reactions of this kind that we must attribute those 

 gradual passages of Iherzolite to pyroxenic or amphibolic rocks, of which the 

 Pyrenees present examples at many points.* 



TRANSFORMATION OF SERPENTINE INTO LHERZOLITE OR INTO PERIDOT. 



THEORETICAL DEDUCTIONS. 



There is another magnesian rock which it is proper to place near the peridot 

 and the Iherzolite, notwithstanding the differences which separate it from these 

 last. Serpentine presents itself among eruptive rocks, with exceptional charac- 

 ters, as being at once hydrated, infusible, aud without distinct crystallization. 

 Geologists admit, generally, that serjtentine resuhs from the transformation of 

 another rock, and that it is derived frcmi peridot, at least in certain cases where 

 it has preserved the characteristic form of the crystals of that substance. 



Deferring the realization of sei'pentine from peridot as being at the present 

 moment impracticable, I have been content to follow the inverse order, that is, 

 to transform serpentine into peridot. Here the relative composition of the two 

 minerals pointed out the course to be pursued ; the serpentine di tiers from peridot 

 only in containing water and including more silicium or less magnesium. It was 

 requisite, therefore, to fuse the serpentine with the addition of magnesium in order 

 to realize the constitution of peridot. 



By treating in this manner the serpentines of Snarum, in Norway ; of Monte- 

 Ferrato, in Tuscany ; of Sainte-Sabine, in the Vosges ; and of Gaito, in 

 Isera, I obtained, after fusion, masses confusedly crystalline and oflering in raanj' 

 of their parts all the characters of peridot. Needles of enstatite are frequently 

 disseminated therein or cover the surface. Tlie presence of this bisilicate is 

 explained by the fact that the specimens operated upon might include a little 

 more silicium than the type of the formula (Mg^ Si*) with which I had started. 



These results have led me to examine the product of the pure and sim})le fusion 

 of serpentines. The experiment made, in crucil)les of earth, on specimens of 

 different origin (Snarum, in Norway; Zoeblitz, in Saxony; Favero, in Pied- 

 mont) has also yielded mixtures of peridot and of enstatite, tliough, in these, tlie 

 former mineral appears in smaller proportion than in the fusions inade in pies- 

 ence of maguesium. The serpentine of Baldissero, in Piedmont, known by the 

 veins of magnesium and resinite quartz which it has secreted, has presented the 

 result best characterized ; needles of enstatit-e grouped with remarkable regularity, 

 parallel with one another and in clusters, detach themselves In the midst of the 



* De Charpentier, Essai sur la constitution gcognostique des Pyren6es. 



