[ m8 ] 



contad were fo much the more numerous as its height was greater, 

 thereby determined thefe portions to a fimilar depofition, until 

 the diminilhed denfity or exhauflion of the menftruurn dimi- 

 nifhed or put an end to the number and extent of the points of 

 contad of the depofited maffes with the foUds contained in the 

 menftruurn. In fome cafes alfo, particularly after the chaotic 

 fluid was heated by the caufcs already mentioned, and a confider- 

 able evaporation had enfued, the cryftallization might have begun 

 at the furface, as we fee happen to fome falts and to lime-water. 

 Thus extenfive ftrata might have been fucceffively depofited, 

 moftly in an horizontal, but often from accidental ruptures during 

 their fall, in an oblique or nearly vertical pofition. Thus far we 

 are led by general analogies, without the aff.ftance of romantic or 

 gratuitous hypothefes, and the view of the fubjed thus obtained 

 is fufficient for the explanation of moft of the obfervations hi- 

 therto made on the ftrudure of primitive mountains. 



The formation o{ plains is eafily underftood, in the wide inter- 

 vals of diftant mountains, after the firft cryftallized maffes had 

 been depofited, the folid particles ftill contained in the chaotic 

 fluid, but too diftant from each others fphere of attradion to con- 

 crete into cryftals, and particularly thofe that are known to be 

 leaft difpofed to cryftaliize, and alfo to have leaft affinity to water, 

 were gradually and uniformly depofited. Of this nature argilla- 

 ceous particles are known to be, intermixed as may well be ex- 

 peded with a large proportion of filiceous and ferruginous parti- 

 cles 



