4 



HUTTONIAN THEORY. 



8i. The perfed confolidation of many gra 



■e 





u 



iti 



luites, furnifhes an argument to the fame eiiea;. 

 For, agreeably to what was already obferved, in 

 treating of the ftrata, a fubllance, when cryftal- 

 lizing, or pafling from a fluid to a foiid ftate, 

 cannot be free from porofity, much lefs fill up 

 completely a fpace of a given form, if, at the 

 fame time, any folvent is feparated from it ; be- 

 caufe the folvent fo feparated would Itill occupy 

 a certain fpace, and when removed by evapora- 

 tion or otherwife, would leave that fpace emp- 

 ty. The perfed: adjuftment, therefore, of the 

 Ihape of one fet of cryftallizing bodies, to the 

 fliape of another fet, as in the Portfoy granite, 

 and their confolidation into one maf>, is as 

 flrong a proof as could be defired, that they cry- 

 llalilzed from a ftate of fimple fluidity, fuch as, 

 of all know^n caufes, heat alone is able to pro- 

 duce. 



I 



82. This concluflon, however, does not refl: 

 on a fingle clafs of fads. It has been obferved 

 in many inftances, that 



where jrranite and itra- 



granite a 



m 



tified rocks, fuch as primary fchiftus, are 

 contad, the latter are penetrated by veins of the 

 former, which traverfe them in various direc- 

 tions. Thefe veins are of different dimcniions, 



r 



fome being of the breadth of feveral yards, others 

 cf a few inches, or even tenths of an inch ; 

 they diminifli as they recede from the main bo- 



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