TrLOR QUATEENAllY GEAYELS. 63 



The gravel is 50 feet above the river Aire in the thickest part ; and 

 no rock has been met with to prove how mnch lies below the level of 

 the river-bed ; but the town surveyor, who has carried out the 

 drainage of that town, informs me that the rock is probably from 

 30 to 40 feet below the level of the river. 



Considering the width of the vallej'-, nearly three-fourths of a mile, 

 we might estimate the gravel over a width of 1000 yards to be of 

 an average thickness of 20 yards ; 20,000 yards at a weight of 

 IJ ton to the cubic yard, is 30,000 tons; there would be then 

 30,000 tons of rock and gravel to each yard run, or about 53 million 

 tons of gravel to each mile of river, supposing the section, fig. 3, at 

 Bingley to contain the average amount of gravel in that valley. 



This quantity of 53 millions of tons of gravel per mile is appa- 

 rently not out of proportion to the power and dimensions of a river 

 able to flood its valley to a height of 50 feet over a surface a 

 mile wide with a gradient of from 3 to 10 feet per mile. 



The escarpments, or gravel-banks, 50 feet high and 200 yards 

 wide, in fig, 4, appear to mark the ordinary limits of the ancient 

 river, as the sides of the gravel-bank are laid in many parts in the 

 form of a steep escarpment sloping to the current at an angle of from 

 25° to 35°, while the top of the gravel-bank is flat, except where it is 

 hollowed out by another part of the river-channel more or less 

 deeply. A bank of 10 feet above the Aire is sufficient now to retain 

 the water, except in the heaviest floods. Contrasting the floods of 

 this river at the present time with those in. the period when the 

 gravels were deposited, it would appear that a flood-Kne of 10 feet 

 now replaces one of 50 feet. The cubes of these flood-lines would 

 probably represent the proportion of the volume of water flowing 

 down the valley in the two cases. Then 10'^ is to 50^ as is 1 to 125. 

 The volume of water would on that hypothesis now be only the 

 YYK ^^ ^^^^ ^^ ^^® gravel-period. 



Section (PI. lY. fig. 5) along the line C D, through Eye-Loaf Hill, 

 one mile E.S.E. of Bingley, shows the outline of the gravel-deposit 

 lying on Carboniferous sandstone and shales. This part of the 

 Aire gravel, along the line C D, reaches also to a height of 50 feet 

 above the present level of the river; it does not appear to have 

 ever been worked for limestone, and is about the same height above 

 the irver Aire as in A B. The escarj)ment of the gravel at Rye- 

 Loaf Hill is well marked, and slopes to the river at 25° ; the top is 

 flat, and the form such as could only be produced by a river occupy- 

 ing during floods the whole width of the valley, the water rising at 

 least 50 feet above the present flood-level. The limestone boulders 

 forming a large portion of the Bingley gravel are so well rounded 

 that they indicate long-continued rolling in a river-channel. 



There is a swamp to the east of Bingley church, in which remains 

 of oak-trees have been found in peat, and below the surface a stratum 

 of freshwater shells of existing species, according to my informant. 

 This part of the section appears to be identical with the Hippo- 

 potamus-bed at Leeds. 



Mr. A. Harris, jun., of Ashfield, found, in 1868, pieces of rolled 



