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sed to view in a solid mass, with little or no appear- 

 ance of a superincumbent decomposed matter. 



Hence, it seems that this appearance in rocks, 

 though similarly situated, is not general. Therefore 

 could not have been the result of a chemical decompo- 

 sition from the infiltration of any menstruum from 

 the surface of the earth. 



The instances in which those appearances occur, 

 seem to be mostly confined to stratified or schistose 

 rocks ; and as they are thus found at various depths 

 in the earth, I am disposed to consider it as the result 

 of an imperfect formation a consequence of the min- 

 eralizing powers acting with less force near the sur- 

 face of the ridge of rocks, (though at a great depth in 

 the earth) than below, where the deposition, or crystal- 

 lization commenced. Of this, if we consider the for- 

 mation of rocks as the result of deposition, or crystal- 

 lization, we shall find analogous cases, sufficiently 

 abundant in every chemical laboratory, to justify the 

 conclusion. 



The principal and most efficient cause then, of the 

 decomposition of rocks, appears, without going into a 

 further investigation of the subject, to be the following 

 degrees of temperature, viz. moist, or wet and dry, 

 heat and cold. 



The effects of these, on a variety of species of rocks, 

 is too obvious and palpable to be denied. But how- 

 few are they ? What proportion do they constitute 

 of the great mass of rocks that compose the outer crust 



