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HUTTONIAN THEORY. 



28 



r 



tion of fabterraneous lieat, is clay in fome Hate 



or 



other, and probably in that of argillaceous 



fchiftus. It follows, of confequence, that ar- 

 gillaceous fcliiilus may by heat be converted in- 

 to whinllone. When, therefore, melted whin- 



ilone has been poured over a rock of fuch fchif- 



r 



tus, it may, by its heat, have converted a part of 

 that rock into a ftone limilar to itfeif • and thus 

 may now feem to be united, by an infenfible grada- 

 tion, with the ftratum on which it is incumbent : 



and phenomena of 



kind may b 



peeled 



P 



have really happened, though but rarely 

 rticular combination of ( 

 ceffary to produce them. 



(t 



fee 



Hence it is evid 



that ftones may graduate into one another, with- 

 out being of the fame formation ; and that it is 

 fallacious to conclude, from the infeniible tran- 

 fition of one kind of rock into another, without 

 any other circumftance of affinity, that they have 

 both the fame origin. 



I am difpofed, therefore, to make fome limi- 

 tation to what is faid in § 72, wdiere I have ex- 



prelTed an abfolute incredulity as to fuch tranii- 

 tions as are here referred to. The areat fkill 

 and experience of the mineralogift'who has de- 

 fcribed the llrata at Scheibenberg, do not al- 

 low us to doubt of his exadnefs, though fome 

 of the appearances are fuch as decompoiition 

 ^nd wearing might well enough be fuppofed to 



produce. 



/ 



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