AND ANALOGIES, OF ROCkS. 201 



granite from solution in water, is incompatible, equally, 

 with its mineral and geological characters and with 

 the laws of chemistry; because negative arguments 

 can have no weight with those who form, what are 

 popularly called opinions, without evidence, or against 

 it. To the insolubility of the earths, and to the im- 

 possibility of thus producing a simultaneous and con- 

 fused crystallization, it is unnecessary to add that of 

 the abstraction of the solvent. Those who have re- 

 torted on the theory of consolidation from igneous 

 fluidity, that quartz is not fusible, have only shown 

 that ordinary ignorance of chemistry which has at- 

 tended most of these disputes; by not knowing that 

 the earths separate from the general mass, to form 

 minerals, according to the laws of chemical affinity. 



Thus, from chemical analogies, there is assigned to 

 all the unstratified rocks, that origin which was already 

 deduced from various other considerations: and thus 

 there is proved to exist a division of rocks formed 

 exclusively by the agency of heat. It will now be 

 convenient to begin the remainder of this examination 

 at the other extreme* 



Where water holding carbonat of lime in solution 

 is gradually evaporated, there are formed calcareous 

 concretions which often attain a great size through 

 age, and which, under peculiar circumstances of cry- 

 stallization, are sometimes not very different in aspect 

 from certain limestone rocks. Under different cir- 

 cumstances, similar waters deposit their contents, so 

 as to form rocks of great depth and extent, producing 

 veal calcareous strata. The Travertine of Italy ap- 

 pears to be one of the most perfect examples of this 

 nature. These simple and recent calcareous rocks 

 become compounds, in cases where the calcareous 

 solution lias entangled fragments of shells, as it does 



