of the Cumbrian Mountains. 59 



to the carboniferous chains of the North, took place during a time long an- 

 terior to the principal dislocations of our south-western coal-fields*. 



Fourthly. Though the contortions of the carboniferous system of the 

 Bristol Channel are so very extraordinary^ the actual elevation of the beds is 

 much less than that of the northern chain. This is perhaps the reason why 

 the secondary rocks, from the new red sandstone to the chalk,, have in their 

 range from the south coast to the latitude of Derby, a direction nearly parallel 

 to the mean bearing of the grey wacke chains — that is, the very direction they 

 would have had, provided they had been deposited immediately on the flanks 

 of the grey wacke chains, without the intervention of the carboniferous series. 

 Thus, for example, the principal line of transition limestone in South Wales 

 is nearly parallel to the direction of the great oolitic terrace in the corre- 

 sponding latitudes. In making this observation (which must not be pushed 

 too far), all minor inequalities are, of course, left out of account, as well as the 

 changes of bearing produced by much more recent disturbing forces — such, for 

 instance, as the great saddle of the wealds of Kent, and the east and west range 

 of the vertical chalk through the Isle of Wight and a part of Dorsetshire. 



Now if we follow the same secondary beds beyond the latitude of Derby, 

 we find a sudden change in their direction, bringing them nearly into paral- 

 lelism with the great central carboniferous chain of the North. From which 

 it appears, that this chain was of sufficient magnitude to produce, by its eleva- 

 tion, a great change in the bottom of the neighbouring seas, and, conse- 

 quently, to produce an immediate influence upon the direction of all the strata 

 afterwards deposited, by the same seas, upon its flanks. 



Leaving the consideration of subjects which may appear remote and hy- 

 pothetical, I now proceed to describe the nature of some of the greater dislo- 

 cations produced by the elevation of the northern carboniferous chain. The 

 disturbing forces, acting with their greatest intensity in a direction nearly 

 north and south, commenced in the latitude of Derby, and produced their 

 first effects towards the north in elevating the High Peak limestone and the 

 coal-fields on its eastern flank. They are marked by a system of great lon- 

 gitudinal faults ranging on the west side of this limestone region f. 



* I am aware that this conclusion has been objected to by some of our best geologists, but I 

 do not believe that they have personally examined the whole evidence on which it rests. 



T ^^^ PI* V. fig. 1. Some interesting phenomena connected with these faults are described 

 in Farcy's Geological and Agricultural Survey of Derbyshire. The accompanying section is 

 not intended to convey any details of stratification, but only a general notion of the position of 

 the great mineral masses. The toadstone beds of the High Peak limestone are intentionally 

 omitted. 



