Vol. 70.] GLACIAL GEOLOGY OF EAST LANCASHIRE. 207 



quarter of a mile north of the actual watershed between the Irwell 

 and Calder basins, at an altitude of 925 feet above O.D. 



Along the western slopes of the Pennines, the limit of the North - 

 Western Drift attains a maximum altitude of 1375 feet west of 

 Blackstone Edge, and falls northwards and north-westwards to the 

 eastern edge of the Walsden gorge. 1 The way in which the limits 

 of the North- Western Drift terminate opposite to each other on 

 the gentler slopes above the gorge is very striking, especially as 

 nowhere in the whole area can the passage of North- Western into 

 Local Drift be more clearly demonstrated than in this neigh- 

 bourhood, the erratics being numerous and of moderate size close to 

 the limit of then- distribution. 



Boulders of igneous rocks have been recorded from several 

 localities in the Walsden gorge, as far as Todmorden and all down 

 the Calder Valley 3 ; but the deposit of tough blue clay with big 

 striated boulders of the North- Western type found at Millwood 

 (Todmorden gasworks) is of greatest significance 3 for our purpose. 



[My own mapping of the Drift was not carried more than a mile 

 or two south of Blackstone edge. The following statement by the 

 late C. E. De Ranee with reference to the district farther south 

 has an important bearing upon the general problem : — 



* Fragments of sea- shells [occur] up to 1280 feet and granites from the South- 

 West of Scotland and 7-foot boulders of andesites from the Lake District at 

 1330 feet. Westward of the Pennine Axis the Glacial Drift rises to [the 

 1250-foot contour] or somewhat above it in both Lancashire and Cheshire ; 

 eastward, though lower elevations may occur, the Drift is conspicuous by its 

 absence.' (Trans. Manch. Geol. Soc. vol. xxii, 1892-93, p. 51.)] 



(3) Winter Hill.— The hill-country west 4 of the Irwell Valley 

 is everywhere covered by North- Western Drift, with the exception 

 of its highest point, Winter Hill, 5 north of Bolton. North- Western 

 Drift occurs up to over 1460 feet on the north-west of this hill, 

 and its maximum altitude diminishes on both sides of the hill 

 towards the south-east, where it extends only to about 1300 feet 

 above O.D. 



(iii) The distribution of the Local Drift. — It has been 

 shown above how the foreign Drift passes insensibly into Drift in 



1 E. W. Binney, 'Additional Notes on the Lancashire Drift Deposits ' Proc. 

 Manchester Lit. & Phil. Soc. vol. xi (1872) p. 139 ; R. Law, in report on ' Erratic 

 Blocks of the British Isles ' Proc. Brit. Assoc. (Liverpool) 1896, p. 371. 



2 J. W. Davis, ' Erratic Boulders in the Valley of the Calder ' Proc. Yorks. 

 Geol. Soc. vol. vi (1875-79) pp. 93-98 ; J. Aitken, ' Drift Deposits on the 

 Western Pennine Slopes, &c.' Trans. Manch. Geol. Soc. vol. xiv (1876-78) 

 pp. 51-56; and B. Law & W. Simpson, 'Report on the Drift Deposits at 

 Mytholmroyd ' Proc. Yorks. Geol. Soc. n. s. vol. xiv (1901) pp. 231-36. 



3 J. Spencer, ' Halifax Naturalist' vol. i (1896) pp. 21-25 & 45-49. 



4 J. Aitken, ' An Outlier of Drift-Gravel on Holcombe Hill ' Trans. Manch. 

 Geol. Soc. vol. vii (1868) p. 57; 'High-Level Drift in the Neighbourhood of 

 Bacup' ibid. vol. xiii (1874-76) p. 135. 



5 E. Hull, ' The Geology of the Country around Bolton-le-Moors (Lanes.) ' 

 Mem. Geol. Surv. 1862, p. 29. 



