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structure, both on the small and large scale ; as in 

 granite, trap, pitchstone, and certain limestones ; 

 but these are more particularly mentioned in other 

 places. 



The lamellar structure is sometimes detected 

 by modifications of colour, even when the la- 

 mellae cannot be separated. It is also discovered 

 in some cases by the action of the weather, even 

 when that does not produce the effect of separat- 

 ing the plates ; the edge of one lamella yielding 

 more readily to its impression than another. This 

 occurs in the sandstone of Strathaird in Sky. 



A lamellar structure may however be indicated 

 by the action of the weather, when it has in fact no 

 existence. This happens in granite, where masses 

 of this rock of artificial forms, are found to exfo- 

 liate in solid crusts. 



Examples of the lamellar structure on the large 

 scale, are found in granite ; on a small, in the 

 , rocks of the trap family. In this case it has been 

 called, with some inconvenience, schistose. 



The small lamellar structure occurs in pitch- 

 stone ; and the contorted, both in that rock and 

 in basalts. 



