TRANSACTIONS OF SECTION C. 755 



In the lower branch of the valley we find abundance of fj^lacial materials, which 

 have been pushed up from the Aire by a branch of the Airedale glacier, and 

 among the rocks abundance of limestones. 



In the npper valley we do not find the same state of things; but, instead of the 

 limestones, are grits and sandstones, except along a line commencing at Leventhorpe 

 Hall (which is about three miles from the centre of the town), and passing through 

 Lidget Green, Grange Estate, Little Horton to Bankfoot, it forms a fairly straight 

 line, about tliree-quarters of a mile south of the Town Hall, at its nearest point. 



Behind Grange lioad, to the south, there is an extensive deposit, which has 

 been exposed to a depth of twenty-two feet in some places, and excellent oppor- 

 tunities afforded of examining the boulders, among which were found many speci- 

 mens of limestones, light-coloured and dark, banded and cherty, also a fair quantity 

 of Silurian grits. 



I afterwards found limestone at Hewenden, and Mr. Muff found it near Oxen- 

 hope ; there is also an immense deposit at Cowling. 



Thus -we find the same kind of deposits along a moderately straight line on the 

 south side of the Aire Valley. 



The presence of the Silurian pebbles appears to indicate that, as there is no 

 rock on the south of the Aire from which they could be derived, the Ilibblesdale 

 ice "was forced over into Airedale, and that the moraine formed from tho grits and 

 slates of Ingleborough became the southern one in the Aire Valley. 



The grit boulders to the south of this line are of the same character as the 

 strata forming the hills on that side of the valley, and were probably carried by 

 smaller local streams of ice. 



4. On a Glacial ' Extra-morainic ' Lake occupying the Valley of the 

 Bradford Beck. By J. E. Wilson. 



In the paper read by the late Professor H. Carvill Lewis before the Geological 

 Section at Manchester in 1887 on the Extra-morainic Lakes of Central England 

 and elsewhere, he pointed out that the Aire glacier was the cause of three lakes — 

 one in the neighbourhood of Skipton, towards Bolton Abbey; one due to the 

 damming up of the Bradford Beck ; and one in the valley of the Worth. The present 

 paper is the outcome of an endeavour to verify these observations of Professor 

 Lewis. The proof of the existence of the Aire glacier and of its extension need 

 not detain us further than to point out out that glacial strife occur on both sides 

 of the Aire Valley, and are seen about the outlet of the Bradford Beck at Wind- 

 Iiill, and that boulder clay containing scratched limestones is frequent in the Brad- 

 ford area. Any glacier in the Aire Valley which extended on to the slopes of 

 Idle Hill, the northern point of the ridge which bounds the Bradford basin to the 

 east, would block up the mouth of the Bradford Valley. This ridge has an altitude 

 above the sea at Idle Hill of 750 tVet, and gradually decreases in heio-ht as far as 

 Laisterdyke, afterwards rising again to the southward. The lowest point of the 

 lip of the Bradford basin is marked by the dip through which the Great Northern 

 Railway extends out of Bradford at Laisterdyke. In the event of a block in the 

 valley between Heaton and Idle Hill this would naturally be the outlet of the 

 lake so produced. The height of the col at Laisterdyke is about 560 feet above 

 the sea. 



It would be very unlikely that one would find in a district like this, either 

 much built over or under cultivation, anything in the way of beaches or terraces. 

 But at several points beds of sand and sandy clay have been observed, and these 

 occur at levels of about 650 feet. The most striking is a deposit of sand and silt 

 showing extremely good current-bedding, on the hill opposite Leaventhorp Mill, 

 towards AUerton, and also in the neighbourhood of tlie mill itself. The mode 

 of its occurrence and its appearance suggest a delta deposit, and it is at exactly 

 such an altitude as would fit with the presence of a lake having an outlet at 

 Laisterdyke. The difficulty occurs, however, that the stream flowing in the valley 

 separating the two patches of current-bedded material has a much smaller drainage 



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