Vol. 70.] GLACIAL GEOLOGY OF EAST LANCASHIRE. 217 



The important corollary follows immediately that, in this locality, 

 the ice-barrier must have been withdrawn very uniformly, and that 

 the chief pauses that may have occurred during its retreat were 

 not merely local, but affected a considerable area. 



It is perhaps unnecessary to state that the connexion between 

 the overflow-channels in an aligned series is usually made through 

 lakes held up by the ice-barrier, although the occurrence of scarped 

 hillsides between one channel and the next, or between two lakes, in- 

 dicates that the connecting-link was sometimes a channel between 

 the ice-edge and the hill-slope against which it was resting. 



(«) The Cliviger Series of Lakes and Overflow-Channels. 



The glacial drainage-channels that cross the Pennines north of 

 Bouls worth Hill have been already described, 1 and Dr. A. Wilmore 

 has dealt with some that occur in the Burnley and Colne area. 2 



A few examples of glacial drainage-channels have been found 

 east of the Pennine watershed in this area. Two occur on 

 Todmorden Lower Moor above the Cliviger gorge, about 1 mile 

 :south-east of Portsmouth ; they do not actually cut through the 

 ridge, but notch its south-eastern slope. Probably the first glacier- 

 lake to be formed in this region was dammed up in a small valley 

 (Paul Clough) opening into the Cliviger gorge about a mile 

 north-east of Portsmouth. It overflowed south-eastwards through 

 what is now a dry gap, at 1000 feet above O.D. With the ex- 

 ception of one or two valleys of doubtful origin, there are no 

 other overflow-channels in the Cliviger gorge south-east of the 

 watershed. 



Whinberry Flat, about three-quarters of a mile south-east of the 

 Gorple gap, is a mass of alluvium which probably occupied the site 

 of a glacier-lake formed when the ice stood at about 1300 feet. 

 The lake had as its outlet a shallow channel directed eastwards. 



Several small overflow- valleys were formed by the direct drainage 

 from the edge of the ice, as soon as it retreated to the west of the 

 watershed : one cuts through solid rock at about 1285 feet on 

 the south-western side of the w T ide col at Widdop Cross, and 

 two parallel channels are cut through the Drift that covers 

 the watershed at the Gorple gap, at about 1275 and 1250 feet 

 above sea-level respectively. 



As soon as the ice retreated west of the Pennines a lake was 

 probably formed at the head of Shedden Clough (west of Black 

 Hameldon). Its waters escaped southwards through a shallow notch, 

 just below 1275 feet O.D., in the ridge between Shedden Clough 

 and the Cliviger valley. Farther west, this ridge is cut by several 

 very characteristic overflow-channels, all draining southwards, and 

 is also frequently scarped where water escaped between the ice 



1 A. Jowett &]H. B. Maufe, Proc. Yorks. Geol. Soc. n. s. vol. xv (1904- 

 1905) pp. 227 & 228. 



• Glacial Geology of Colne & District ' Proc. Colne Lit. Sci. Soc. 1908, 

 pp. 17-20. 



Q2 



