36 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [DcC. 3, 



base of the Pennine chain, has not yet been carefully described* ; 

 and although, during former years, I have followed it through a con- 

 siderable portion of its length, it is not my object to enter on any 

 general description of it in this place. I may, however, remark, that 

 some fragments of the carboniferous series on the western side of the 

 fault are full 2000 feet below what we might call their natural posi- 

 tion in the great Pennine chain. Can we then say, that the Pennine 

 fault ever produces a downcast of 2000 feet on its western side ? In 

 a certain geological sense we might make the assertion correctly ; for 

 on the opposite sides of the fault there is an actual change of the 

 geological horizon amounting to more than 2000 feet. But in the 

 stricter sense in which the word fault is used by miners and prac- 

 tical men, there is never (so far as I have seen the Pennine fault) 

 anything like an upcast or a downcast of 2000 feet. 



In the normal condition of a fault we have a nearly vertical frac- 

 ture ; and, if we can examine the beds immediately on the opposite 

 sides of the fracture, we can. determine correctly the quantity of up- 

 cast or downcast produced by the fault. Such are the faults described 

 in our coal-fields and other mining districts. But in the grander 

 dislocations (such as the Pennine and Craven faults) the lines of 

 fracture are seldom of a simple nature ; and the beds, on the oppo- 

 site sides of the lines of break, have seldom the same dip and incli- 

 nation : and hence it follows, that at a comparatively short distance 

 from the lines of dislocation there may be an enormous change in the 

 geological horizon, mainly produced by a change of dip ; although, 

 at the same time, the upcast or downcast along the actual line of 

 break amounts to a quantity that is comparatively insignificant f. 



I am here stating what is little more than a truism ; yet it has 

 sometimes been lost sight of, if not in the speculations, at least in 

 the language of geologists. To explain my meaning I will quote two 

 instances. Between Brough and the foot of Stainmoor, the disloca- 

 tions produced by the Pennine fault are so complicated that I know 

 not how to represent them ; but in the hills immediately above 

 Brough, the relations of the strata are, I believe, correctly represented 

 by the accompanying section (fig. 1), which crosses the line of the 

 Pennine fault. Close to Brough, and at a low level, are some beds 

 of the carboniferous series, which are, geologically, far above the 

 great Scar Limestone ; but their representatives in the unbroken 

 chain, on the other side of the fault, are at a much higher level, and 



" Craven fault," in reference to the labours of Professor Phillips, as he had pre- 

 ceded me in a description of the southern end of the fault where it passes into the 

 division of Yorkshire called Craven. With some of its phaenomena, in its range 

 from Ingleton to the foot of Stainmoor, I had, however, been familiar for many 

 years ; as it crosses my native valley of Dent, about half a mile below the village, 

 dislocating and setting on edge all the lower limestone beds. These " edge-beds," 

 well known to all the quarrymen of the neighbourhood, greatly affect the external 

 features of the country through which they pass. 



* Dr. Buckland's observations on the dislocated district near Cross Fell appeared 

 in the Trans. Geol. Soc. 1st Ser. vol. iv. p. 105 et seq. 



t These facts are noticed and well illustrated in the paper by Professor Phillips, 

 referred to above. 



