388 



DIAGRAM 



Shewing tlie relative position which the Plutonic and Sedi- 

 mentary Formations of different ages may occupy ; 

 (in illustration of TABLE I.) 



No. 91. 



Tertiary strata. 



4. Recent pliitonic. 



In the above diagram an attempt is made to shew the inverted order in which 

 the sedimentary and pliitonic formations may occur in the earth's crust; subter- 

 position in the plutonic, like superposition in the sedimentary rocks, being for the 

 most part characteristic of a newer age. By aid of this illustration, and what we 

 have said in Chap. 25 and 20, the reader will comprehend why so large a portion 

 of the plutonic rocks of later periods are concealed, and why the more ancient of 

 this class have risen nearest to the surface, so as to have been denuded in some 

 regions and exposed to view. 



* The primary formations here mentioned are those, whether stratified or un- 

 St ratified, which are older than the carboniferous deposits. 



