1868.] hfll — itnes of elevation. 333 



Periods of Denudation. 



First Period. — Having shown, by the evidence of the unconforma- 

 ble patches of Permian beds on the northern flanks of the Pen die 

 range agreeing with the position of the contemporaneous beds in 

 Yorkshire, that the Pendle range had received its earhcst outline 

 at the commencement of the Permian period by the sweeping away 

 of a prodigious amount of material to the north of the range, we 

 cannot suppose that this was a solitary case. On the contrary, it 

 is evident that the main features of the Carboniferous districts of 

 North Lancashire and the North "Riding were first shadowed forth 

 at this same time. 



This leads me to remark also that it is extremely improbable 

 that productive Coal-measures exist under that tract of Triassic 

 and drift-covered ground stretching inland from the coast to Orms- 

 kirk and Blackpool ; for it can scarcely be doubted that the Carboni- 

 ferous rocks under this tract were subjected to the same disturb- 

 ances, and partook of a similar denudation to that which resulted 

 in carrying away the Upper Carboniferous rocks from the vale of 

 Clitheroe. 



If, then, there was a period of disturbance throwing the rock- 

 masses into a series of great folds, ranging from east to west across 

 North Lancashire and Yorkshire, there was a corresponding and 

 concurrent period of denudution, during which enormous masses of 

 Carboniferous strata were swept away from these regions. These 

 flexures died away southward, in which direction the corresponding 

 amount of denudation was very much less, as is proved by the 

 position of the Permian beds along the southern margin of the 

 Lancashire coal-field. As the first movements of the Pennine sys- 

 tem of flexures had not as yet commenced, we may suppose that 

 whatever undulations may have been produced over the region now 

 occupied by the high ranges of Black Hambledon, Blackstone Edge, 

 Pule Hill, Kinder Scout, and the Derbyshire hills took an east 

 and west direction, and were of minor importance in comparison 

 with those which had been developed over North Lancashire and 

 Yorkshire. 



Second Period. — "With the close of the Permian epoch commenced 

 the movements which ultimately gave birth to the Pennine chain of 

 hills, and which, by the denudation of the "Upper Carboniferous 

 rocks across the region of the central axis, caused the disseverance 

 of the Lancashire and Cheshire coal-fields from those of Yorkshire 

 and Derbyshire. To what extent these ranges of hills were subse- 

 quently entombed in Triassic strata is a speculative but interesting 

 question. Eecollecting the enormous vertical development of this 

 formation in South Lancashire and Cheshire, amounting to nearly 

 4000 feet of strata, we may conclude that the Pennine and Pendle 

 hills were encased in these red beds, and that to this protection they 

 owe, to a certain extent, their preservation. 



Third Period. — The thii'd period of denudation was that which oc- 

 curred after theBunter Sandstone had been formed, and is represented 



