76 The Origin of Crystalline Rocks. 



the primitive earth, and at an early time held in solution the 

 whole of the materials of these rocks. The inadequacy of all ot 

 these hypotheses was pointed out, though it was said that 

 Werner's is the one nearest the truth. 



The author conceives that the crystalline rocks were formed by 

 deposition from waters which successively dissolved and brought 

 from subterranean sources the mineral elements. Their formation 

 is illustrated by that of granitic veins and that of zeolites — processes 

 regarded as survivals of that which produced the earlier rocks. 

 The true zeolites are but hydrated feldspars, while the minerals oi 

 the pectolite group correspond to the protoxyd-silicates of these an- 

 cient rocks, often remarkably concretionary in aspect. 



The source of the elements of these rocks, according to the new 

 hypothesis here proposed, was in the superficial layer which was 

 the last congealed portion of an igneous globe consolidating from 

 the centre. In this primitive stratum, porous from contraction, 

 and impregnated with water, resting upon a heated anhydrous 

 nucleus, and cooled by radiation, an aqueous circulation would 

 be set up, giving rise to mineral springs. The water of these 

 dissolved and brought to the surface, there to be deposited, the 

 quartz, feldspars, and the other silicates which, through successive 

 ages, built up the great groups of crystalline stratified rocks. 



Exposed portions of the primitive silicated material would be 

 subject to atmospheric decay and disintegration, giving rise to 

 aqueous sediments of superficial origin, which would become 

 intercalated with the deposits from subterranean sources. The 

 reactions between the mineral solutions from below and these 

 superficial materials were doubtless important in this connection, 

 probably giving rise to certain common micaceous minerals ; while 

 dissolved silicates allied to pectolite, by their reaction with 

 the magnesian salts which then passed into the waters of the ocean, 

 would generate species like serpentine and pyroxene. 



This process of continued upward lixiviation of the primitive 

 chaotic layer would result in the production of a great overlying 

 body of stratified acidic rocks, leaving below a basic residual and 

 much diminished portion, the natural contraction of which would 

 cause corrugations in the superincumbent stratified mass, such as 

 are everywhere seen in these ancient rocks. 



The source of volcanic rocks is partly in this lower basic and 



