Cll. XIIL] THE INCLINED POSITIONS OF STRATA. 275 



sition, experienced successive subsidences, in order to preserve 

 the sea nearly at its present depth. 



But we must return from these speculations to a narrative 

 of facts. It has been stated, that the tertiary deposits of 

 Sicily are elevated many thousand feet above the present 

 sea-level ; and, in whatever manner this has been effected, a 

 great part, if not the whole of them, have not undergone any 

 considerable derangement by this change of position. And 

 so it is with numerous marine deposits in various parts of 

 Europe, which occur at great heights above the sea, and yet 

 are arranged in horizontal strata. Now, if these deposits 

 have been raised into their present elevated position by the 

 expansive power of the central fire, it must be admitted that 

 the inclined rocks, on which they rest, have also been exalted 

 to the same extent; that is, that all Europe has been 

 moved by this internal power, without any general dis- 

 turbance in the previous arrangement of its rocks. 



Such is the general condition of rocks which now appear 

 far above the level of that ocean in which they were once 

 submerged. And, before we determine on the nature of that 

 elevation, let us enquire what alteration in the position of 

 the strata has been produced by the intrusion of trap rocks. 



" On the summit of the limestone platform of the Val di 

 Noto, I more than once saw," says Lyell, " dikes not only 

 of lava, but of volcanic tuff, rising vertically through the 

 horizontal strata, and having no connection with any igneous 

 masses now apparent on the surface." * 



Dr. Macculloch, in his account of the trap rocks of Skye, 

 has pointed out the structure of the different kinds, and the 

 nature of their connection with each other. His observations 

 on the trap-veins which traverse the stratified rocks of Strath- 

 aird are particularly important. These veins generally con- 

 sist of a bluish black basalt, which is sometimes porphyritic, 

 and assumes the ordinary appearances of this rock. One of 



* Principles of Geology, vol. iii. p, 70. 

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