'228 dr. a. jowett ox the [June 1 9 14, 



EXPLANATION OF PLATES XXXI-XXXV. 



Plate XXXI. 



Fig. 1. General view of overflow- channels south-west of Knowl Hill; the 

 view is taken looking north-north-westwards. The course of the 

 main channel, indicated by the factory chimneys, runs along the 

 hillside from north-west to south-east, instead of following the 

 direction of steepest slope, north-east to south-west. The channel 

 has a broad flat floor, and is occupied by a comparatively small 

 stream. Thick Drift occurs on the left of this valley. (See p. 221.) 

 2. View looking northwards from nearly the same position as in fig. 1. 

 The flat-topped hill on the sky-line is Knowl Hill (1378 feet). The 

 ridge running southwards from Knowl Hill is cut across by two 

 channels ( — *-) directed eastwards. The higher of these. Wind-Hill 

 Nick, is a dry gorge (PI. XXXII, fig. 1) ; the lower, Birtle Dean, is 

 a continuation of the main channel mentioned above (fig. 1), and is 

 over 200 feet deep. Wind-Hill Nick cuts the ridge at 900 feet, and 

 Birtle Dean at 850 feet above O.D. (See p. 221.) 



Plate XXXII. 



Fig. 1. View of the entrance to the Wind-Hill dry channel, looking south- 

 eastwards. (See also PL XXXI, fig. 2.) This is a beautifully- 

 formed valley, 50 feet deep on the watershed, cut in Millstone Grit. 

 Its floor slopes eastwards, away from the observer. 



The hillside on the left of the picture is scarped, and formed one 

 side of the drainage -channel — the other side consisting, at this point, 

 largely of ice — which carried the water to Wind-Hill Nick. This 

 channel was cut down a little farther, after Wind-Hill Nick was 

 abandoned. It will be noted how the stone wall which crosses the 

 floor of the channel is partly hidden by the low right bank. (See 

 p. 221.) 

 2. View, looking south-south-westwards, of the lower portion of Ratcliffe 

 Hill dry channel, south of Shore Moor. This channel is over 100 

 feet deep on the watershed, and is directed northwards, all the 

 normal drainage here being directed southwards. The floor of the 

 channel widens, and terminates in a gently- sloping delta at about 

 825 feet O.D., below which the hillside is steeper. The hill on 

 the left is 950 feet above O.D. (See p. 220.) 



Plate XXXIII. 



Map, on the scale of 3 miles to the inch, or 1 : 190,080, illustrating the 

 distribution^of the three types of Drift in East Lancashire. 



Plate XXXIV. 



Map, on the scale of 3 miles to the inch, or 1 : 190,080, indicating the chief 

 •overflow- channels (shown in red) and the various positions of the edge of the 

 ice at its maximum extension, and at well-marked stages during its retreat. 

 [For ' Black Hameedon' read ' Black Hameldon.'] 



Plate XXXV. 



Reduction, on the scale of about 5 miles to the inch, or 1 : 316,800, of the 

 above-mentioned map (PI. XXXIV), showing the glacier-lakes and overflow- 

 channels in existence at the more important episodes during the retreat of the 

 ice- sheet. 



