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position, and the effects which it produces in 

 modifying their characters. It appears to exist 

 in at least four distinct assignable states, that of 

 the peroxide, the protoxide, the carbonat, and 

 that combination of the carbonat with water which 

 forms rust. 



BITUMEN. 



This must also be considered as a constituent 

 of some rocks, from the remarkable character 

 which it communicates where it is found. 



PITCHSTONE 



Is only found in the rocks of the same name. 



CHERT. 



This also occurs only in the rock which is 

 here designated by the same term. The Hprn- 

 stone of many authors is compact felspar. 



