\ 
388 
DIAGRAM 
Shewing the relative position which the Plutonic and Sedi- 
mentary Formations of different ages may occupy ; 
(in illustration of Table I.) 
No. 91. 
4. Kecent strata. 
8. Tertiary 6trata. 
1. Primary* plu- 
tonic. 
2. Secondary plu- 
tonic. 
3. Tertiary plu- 
tonic. 
4. Recent plutonic. 
In the above diagram an attempt is made to shew the inverted order in which 
the sedimentary and plutonic formations may occur in the earth's crust; subter- 
position in the plutonic, like superposition in the sedimentary rocks, being for tbe 
most part characteristic of a newer age. By aid of this illustration, and what we 
have said in Chap. 25 and 26, 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 tin- 
stratified, which are older than the carboniferous deposits. 
