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and in the same manner, in all directions. In 

 certain cases, it is true, they are actually schistose, 

 or rather, laminar ; but the laminae are, in this 

 Case, produced by the progress of disintegration, 

 and that structure does not, as in the argillaceous 

 schists, pervade the whole stone. However dif- 

 ficult to describe the peculiar aspect by which 

 they may be recognized, so as to satisfy the stu- 

 dent who has never seen them; when once 

 known, they can never be confounded again with 

 any other rock. 



The same remarks may be made on basalt, 

 some of the varieties of which may also be known 

 by consisting, or appearing to consist, of horn- 

 blende in a much more minutely granular and 

 compact state than it ever occurs in hornblende 

 schist. 



The granitic division offers peculiar diffi- 

 culties ; as it is in this, that the frequent resem- 

 blances to some of the varieties of granite occur. 



In the first place, all those which contain 

 either augit or hypersthene, may be safely re- 

 ferred to this family. So may those which con- 



