292 AN ENQUIRY INTO THE NATURE OF [Ch. XIIL 



next the granite, are stated, in some places, to dip at moder- 

 ate, and in others, at considerable angles, sometimes from 

 the granite, and at others towards this rock ; so that, if con- 

 tinued, they would either abut against, or underlie the 

 granite. The same statements have been made by Maccul- 

 loch, and other writers. Now, considering the hitherto un- 

 defined nature of the term stratum, we would enquire whether 

 it is probable, that geologists have always selected the same 

 denomination of planes ? and whether they may not have 

 regarded as the strata, sometimes one series of planes, and 

 sometimes another ; of which there are three series ; one per- 

 pendicular, and two others variously inclined, as described in 

 the chapter on the structure of the primary slates. May not 

 this have happened, in some cases, from one set of planes 

 being occasionally more distinctly developed than the other ? 

 or from the degradation, in cliffs and similar places, not 

 having been always confined to the same direction, having 

 been more extensive in one than another, and vice versa ? 

 Lastly, we would ask, if these strata have been upheaved by 

 the granite, how comes it to pass, that whichever series of 

 planes be adopted as true strata, that, in Cornwall, the lines 

 or seams which mark these planes are continued into the 

 granite itself, dividing this rock into corresponding layers? 

 This fact is not obscurely indicated on a single spot, but is 

 displayed, in many places, in clear and bold characters, which 

 cannot be mistaken ; and which certainly cannot be recon- 

 ciled with the idea of the forcible elevation of the strata, and 

 of the protrusion of the granite. 



On the grounds detailed in this chapter, we therefore con- 

 clude that the inclined position of strata is not an infallible 

 criterion of mechanical elevation ; that this appearance in the 

 primary slates may be more justly attributed to their original 

 structure, and in many of the secondary strata to the same 

 cause conjointly with their deposition on inclined surfaces; and, 

 that the notion of granite having been protruded through and 

 tilting up the strata, either in a fluid or solid state, does not 



