SO 



NEWER PLIOCENE PERIOD. 



[Ch. VII. 



This theory of the intrusion of the basalt is confirmed by the 

 fact, that in some places the clay has been greatly altered, and 

 hardened by the action of heat, and occasionally contorted in 

 the most extraordinary manner, the lamination not having been 

 obliterated, but, on the contrary, rendered much more con- 

 spicuous by the indurating process. 



The annexed wood-cut (No. 15) is a careful representation 

 of a portion of the altered rock, a few feet square, where the 

 alternate thin laminae of sand and clay have put on the appear- 

 ance which we often observe in some of the most contorted of 

 the primary schists. 



No. 15. 



Contortions in the newer Pliocene strata, Isle of Cyclops. 



A great fissure, running from east to west, nearly divides 

 the island into two parts, and lays open its internal structure. 

 In the section thus exhibited, a dike of lava is seen^ first cut- 

 ting through an older mass of lava, and then penetrating the 

 superincumbent tertiary strata. In one locality ^ the lava rami- 

 fies and terminates in thin veins, from a few feet to a few inches 

 in thickness (see diagram No. 16). 



