20 THE GEOLOGICAL AGE OF CENTRAL AND WEST CORNWALL. 



and especially in West Cornwall. These are as follows : 



1st. — A general similarity of Mineralogical character in all the 

 stratified rocks of whatever age they may be, resulting from the 

 great amount of metamorphism to which the whole series has 

 been subjected. This is true generally, since nearly all the rocks 

 now visible at or near the surface have been at one time buried 

 deeply under miles of rock, which has since been denuded away ; 

 it is also true locally owing to the number of intrusive rock- 

 masses, and the almost innumerable mineral veins. 



2nd. — Frequent obliterations, or atjeast maskings of stratifica- 

 tion by " cleavage " and by " cross-bedding." 



3rd. — Numerous disturbances, by faults, sometimes very large, 

 but generally of comparatively small amount. In some neigh- 

 bourhoods these dislocations of the strata are so numerous, and 

 their final result is so complicated, that the whole region partakes 

 of the character of a gigantic breccia, as in the example sketched 

 from Penhalls Mine, in the parish of St. Agnes, at a depth of 



50 fathoms below adit.* 

 s 



4th. — Numerous overturns of the strata at the surface — the 

 rocks at their outcrop very commonly dipping down hill, whatever 

 the real dip of the strata may be. This feature is particularly 

 well seen in the quarry behind Erisey Terrace, at Falmouth. 



5th. — Absence of fossils of any kind from the greater part of 

 the area in question, and rarity of distinguishable species even 

 in the best known fossiliferous localities. 



* For this diagram I am indebted to my friend Mr. Alfred Davies, formerly of 

 St. Agnes. 



