Vol. 70.] GLACIAL GEOLOGY OF EAST I/ANCASHIBE. 203 



through which it passes into Yorkshire. Good sections of Kibbles- 

 dale Drift, with striated boulders, occur on the slopes of the Widdop 

 valley for at least a mile south-east of the Pennine watershed at 

 Widdop Cross. According to the late James Spencer, 1 limestone 

 boulders crossed by this route into Yorkshire, and were scattered 

 over the moorlands down to Wadsworth Moor, nearly 3 miles 

 farther east. 



Ribblesdale Drift also extends continuously across the Pennine 

 watershed at the Gorple gap, reaching limits of 1510 feet above 

 CD. on the hill to the north, and on Black Hameldon to the south 

 of the gap. Excellent sections in the same Drift may be seen for 

 half a mile across the Pennine divide on the north-eastern slopes 

 of Black Hameldon, but the Drift appears to be thinning out 

 eastwards. South of Black Hameldon, the Ribblesdale-Drift limit 

 falls rapidly towards the northern edge of the Cliviger gorge, 

 although on the high ground the Drift forms a thick cover extending 

 for nearly 2 miles to the south-east of the watershed between the 

 basins of the Lancashire and Yorkshire Calders. The sides of 

 the gorge are very steep, and landslips and talus have removed or 

 obscured whatever traces of Drift may have originally existed ; but 

 limestone-boulders have been recorded 2 from 18 feet below the floor 

 of the valle3 r at Lineholme, a mile north-west of Todmorden. Blue 

 clay, with chert and big boulders of grit and Grannister, occurs at 

 Hare Hill, over half a mile nearer Todmorden, at 475 feet above 

 O.D. and about 50 feet above the floor of the valley. 



On Lower Moor, south of the Cliviger gorge, the limit of the 

 Ribblesdale Drift extends to within less than 2 miles of Todmorden. 

 Its altitude increases westwards to over 1350 feet, diminishing 

 farther west to below 1325 feet, where it crosses the watershed 

 between the basins of the Yorkshire Calder and the L T pper Irwell. 

 The Drift-limit does not extend far down the L T pper Irwell Valley, 

 terminating about a mile north of Bacup ; although in the floor of 

 the valley it may continue a little farther south, under a more 

 recent deposit of gravel and silt. It then crosses the watershed 

 westwards into the White well Brook valley, turning southwards and 

 attaining an altitude of nearly 1300 feet on a westward projecting 

 spur. Farther south its altitude decreases to below 1100 feet north 

 of Stacksteads, where it is crossed abruptly by the northern 

 "boundary of the North- Western Drift in the Irwell Valley. The 

 rest of the boundary between the Ribblesdale and the Local Drifts 

 lias been obliterated by the deposition of the North- Western Drift. 



Within the extreme limit indicated above, the Ribblesdale Drift, 

 on the whole, increases in abundance as one proceeds from its 

 margin towards its source. It is generally thin on the ridges of 

 solid rock, but has accumulated in the hollows except where sub- 

 sequently removed by stream-action. Thus, it is quite abundant in 

 the upper portion of Green's Clough, 3 miles west-north-west of 



1 * Erratics of the Calder Valley ' Halifax Natiiralist, vol. i (1896) p. 48. 

 3 Ibid. loc. cit. 



