756 REPORT — 1900. 



area than Thornfcou Beck, of whlda it is a tributary, and ia the Thornton Beck 

 Valley similar deposits are very poorly represented. 



To explain this a consideration of the lakes to the westward is necessary. 

 Althouo;h Professor Carvill Lewis only inferred lakes in the Bradford area and in 

 the Haworth area, there is a valley — that of the Harden Beck — ^between them, 

 which also maintained its lake. The Uhellow Dean reservoirs of the Bradford 

 Corporation are situated in a deep narrow valley, the rivulet originally flowing 

 down it having its rise in a drainage area of only about three-quarters of a mile 

 equare, an area wholly inadequate to account for the valley. Its upper part is in 

 fact a deep notch in the ridge, which would form the outlet of the Cullingworth 

 lake, and is at a height of 720 feet. The presence of this lake would account for 

 bads of current-bedded silt at Sandbeds, near Cullingworth, at exactly this level. 

 But in the valley below Chellow Dean hardly any traces of delta deposits have 

 been observed at the level of Lake Bradford — that is, on the same level as the 

 Leaventhorp beds. If, however, the extension of the Aire glacier blocked up the 

 notch at Chellow Dean, the outlet of the lake would be at the next lowest col — 

 that near Stream Head Farm, 870 feet above the sea. The valley below Stream 

 Head Col soon becomes a deep narrow gorge similar in many respects to that at 

 Chellow Dean, and it is on either side of this valley, when it reaches the level of 

 Lake Bradford, that the delta deposit above referred to is found. The position of 

 this large deposit would therefore be explained if it is regarded as the result 

 of the erosion of the valley above by the water from the extensive drainage areas 

 of the Worth and Harden Beck pouring over the Stream Head Col. The material 

 carried down by the beck and arrested in its course on reaching Lake Bradford 

 would be deposited just where the Leaventhorp beds occur. Corroborative evi- 

 dence of the presence of a lake at the level of the Stream Head Col is possibly 

 provided by the occurrence of current-bedded sand exposed in a gravel pit at 

 Hallas Rough Park at about the level of the col. 



On the other hand, the absence of delta deposits from the Chellow Dean Beck 

 would be explained if it is ciinsidered that possibly, when the extension of the 

 glacier was such that the Chellow Dean Col was open, the size of the glacier was 

 not sufBcient to wholly block the mouth of the Bradford Valley. In this case the 

 water would escape by its present outlet, and no lake would exist to arrest the 

 material brought down from the ravine of Chellow Dean. 



At the period when the Chellow Dean Col was open there would be two lakes 

 to the westward, one in the Cullingworth Valley, above mentioned, and one in the 

 Worth Valley. The outlet of the latter would be a deep notch at Sugden End, 

 near Haworth, at 720 feet ; but as the Stream Head Col is at a greater height than 

 this, the two lakes would be merged into one large lake when the Chellow Dean 

 Col was blocked, so that for this period Professor Carvill Lewis's theory would 

 be correct. 



5. A Preliminary Note on the Glaciation of the Keighley and Bradford 

 District. By Albert Jowett, M.Sc., and Herbert B. Muff. 



1. General Vieiu of the Surface Features of the Area. 



The general trend of the Aire Valley in this district is from N.W. to S.E. 

 Actually, the valley makes a number of roughly rectangular bends, receiving a 

 large tributary valley, from the south side, at each southern convexity, viz. : the 

 Glusburu Valley at liildwick, the Worth Valley at Keighley, the Harden Valley 

 at Bingley, and the Bradford Valley at Shipley. The valleys entering on the 

 north side are much smaller. 



The tributary valleys, of which the Worth Valley and the Bradford Valley 

 are the largest and most complex, have been excavated in the plateau of L'pper 

 Carboniferous rocks, of which the Millstone Grit here forms the Pennine water- 

 shed. The altitude of the watershed rarely exceeds 1,500 feet; there is a break 

 below 1,125 feet west of Haworth, and a broader depression below 900 feet 

 between Oolne and Kildwick. The ridges between the tributary valleys, on both 



