204 dk. a. jowett on the [June 1 9 14, 



Todmorden, forming mounds of Boulder Clay full of scratched 

 stones ; whereas, on the highest parts of the ridge, from Heald 

 Moor to Deerplay Hill, it is very thin and (in places) practically 

 absent. On the slope immediately south-west of this ridge it 

 becomes much more abundant 1 ; but, when traced farther south- 

 westwards towards its limit in the Upper Irwell Valley, it again 

 diminishes in quantity. Moreover, wherever the crest of the ridge 

 is slightly lower, a greater accumulation of Drift is found south of 

 the depression. It would appeal', therefore, that this ridge, which 

 attains altitudes of 1419 feet on Heald Moor, 1474 feet on Thieveley 

 Beacon, and 1429 feet on Deerplay Hill, was not far below the 

 limit of the distribution of the Hibblesdale Drift. 



West of Deerplay Hill, at the head of the White well-Brook 

 valley, a wide gap occurs in the ridge, which sinks in altitude 

 to 1170 feet. Hibblesdale Drift is abundant in this gap, 2 and in 

 the northern part of the valley on the south it forms morainic 

 mounds. The high ground west of the head of the Whitewell- 

 Brook valley, though nowhere attaining an altitude greater than 

 1274 feet, has an extremely thin covering of Drift ; but, at the 

 head of the Limy- Water valley farther west, great mounds of 

 Drift 3 packed with scratched limestone-boulders occur. Boulders 

 of the Bibblesdale type are also extremely abundant in the Drift 

 south-east of Accrington, in the lower parts of the Limy- Water,. 

 White well- Brook and Upper Irwell valleys, and also in the main 

 Irwell Valley south of Haslingden and Rawtenstall. 



C. E. De Ranee 4 described Drift with erratics, resting upon Till 

 with limestone and other rocks from the Bolland district at 

 Brinscall. 



These facts indicate that, but for the masking effect of the 

 North- Western Drift, the Ribblesdale Drift would cover a much 

 wider area than that to which it is now restricted. 



(ii) The distribution of the North-Western Drift. — The 

 North- Western Drift covers so extensive an area that it will be 

 more convenient to treat of its distribution in sections, as follows: — 



(1) From Great Hameldon eastwards. 5 — The North- 

 Western Drift extends up the western and northern slopes of Great 

 Hameldon, and a single boulder of Lake-District rock has been 

 found on the top (1343 feet) ; but only Bibblesdale Drift occurs 



1 Mr. H. Bolton, in his ' Geology of Eossendale ' 1890, p. 151, states that 

 ' a good thickness of Boulder Clay has been traced over Heald Moor at an 

 altitude of 1419 feet.' 



2 J. Aitken, ' On Drift Deposits on the Western Pennine Slopes, &c.' Trans. 

 Manch. Geol. Soc. vol. xiv (1876-78) p. 51. , 



3 J. Kerr, ' Traces of Glacial Phenomena in the Valley of the Irwell & ita 

 Tributaries in Eossendale' ibid. vol. x (1870-71) p. 116. 



4 ' The Superficial Geology of the Country adjoining the Coasts of South- 

 West Lancashire ' Mem. Geol. Surv. 1877, p. 7. 



5 T. T. Wilkinson, ' Drift Deposits near Burnley ' Trans. Manch. Geol. Soc 

 vol. iv (1863-64) p. 110; and E. Hull, 'Geology of the Burnley Coalfield 

 Mem. Geol. Surv. 1875, p. 132. 



