m 



ON THE CRYSTALS IN LAVAS. 



IV. 



Observations on the CrystaWtzedSuhsiawces included in Lavas: 

 by G. A. Deluc*. 



Vaiioas con- V OLCANOES occupy such a striking place among ter-* 

 ^•t*"'tr*'Ti' I'estrial phenomena, that they have become the su"bje6t of 

 causes tind ef- numerous conjectures respecting their origin, their influ- 



fects of voka- gfi^e, and the cre'olo^ical consequences deducible from them, 

 noe-s- o o 1 



Wherever natural philosophers or geologists have imagined 

 flavebcen ap- they mi<>ht be called in to found a system, they have made 



plied too geue- , " , .■"'.,,,. 



rally to '•'solo- them act whatever part appeared most suitable to then- pur- 

 ?>'• pose; so that from asimple. and solitary, fact, single of its 



kind, and influencing only the ground occupied, by the vol- 

 cano and its vicinity; and although the volcano resembles 

 only mountains of its own kind,, and in no .respect other 

 JUQuntains, either in shape, coustniction, or coniponent 

 parts; ih^Y have nevertheless concluded, that tlie strata and 

 mountains on the surface of th'e Earth owe their origin to» 

 the action of fire: fire, say they, daily exhibiting to us pro- 

 ductions identical with the primitive rocks of our globe. 

 Crystals in lava Hence it is, that these naturahsts consider the different 

 tornudiiiit (^vystals included in lava, not as products in the humid way 

 a.nterior to the lava, that existed in the strata which the 

 volcanic fires brought into a state of fusion, but as crystal- 

 lizations formed in the lava itself, and frOm its substance, 

 by the slow refri'geration of the mass. 

 Tins tbe foini- On this. opinion chiefly is founded the system, which Mr. 

 de Beilevue's Fleuriau de Bellevue has adopted, and lately publishedf, 

 system. respecting the action of the fire of volcanoes, and the for- 



mation of the terrestrial globe, its strata, and its mountains. 

 Simple state- This question, reduced to its most simple terms, is this : 

 have the crystals included in lava been formed in the lava, 

 and from its substance ; or are they foreign to it, and formed 

 anteriorly, in the humid way, in the strata or substances 

 which the volcanic fire reduced to the state of fusion.^ And 



* Journal des Mines, No. 115, p. 5. 

 ■\ Journal de Physiqucj MaVj 1805. 



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