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tinction. This is, the comparatively erect posi- 

 tion of the strata. But, in many instances, the 

 primary strata occupy very low angles, and even 

 assume the horizontal position ; while the secon- 

 dary, are frequently found elevated to angles of 

 considerable inclination. Even were this distinc- 

 tion much more complete, it would not be of 

 universal application ; since, in each class, there 

 is a large division of rocks that are not disposed 

 in strata. 



The next circumstance in which the rocks of 

 the primary class differ from those of the secon- 

 dary, is their nature, or mineral character. 



Many rocks, readily distinguishable by their 

 peculiarity of aspect, occur in the primary class, 

 but are not found in the secondary ; although the 

 rocks of both classes are often composed of the 

 same mineral substances. Others are so distinct, 

 even in their mineral composition, as to have no 

 resemblances in the secondary class. Such rocks, 

 even in detached specimens, indicate, without 

 the necessity of geological investigation, that divi- 

 sion in nature to which they belong. Without 

 considerable experience, however, it is rarely safe 



