THE THAMES FKOM GT7ILDF0ED TO IIEWBTJEY. 35 



abundant in this gravel, and have been fully described by Prof. T. 

 Eupert Jones and Dr. A. Irving. The largest that the writer has 

 seen was, and probably still is, in a pit 374 feet above O.D., a little 

 east of Round Butt at the southern end of Chobham Ridges, the 

 section in which was as follows : — 



1. Earth, 2 feet. 



2. False-bedded sand with small stones, 4 feet. 



3. Gravel, fairly well stratified, 3 feet shown. 



The sarsen-stone probably rested wholly or partly on Upper Bag- 

 shot Sand below the gravel, for it extended through bed 3 up into 

 bed 2. It sloped slightly to the east, and although a fragment had 

 been broken off, measured 14 feet 4 inches x 11 feet 9 inches x 

 4 feet. Close to it was a smaller stone also with an easterly slope. 

 Both were waterworn, as is the case with all sarsens the writer has 

 seen. 



I have examined a number of samples- from different pits on the 

 great plateau, and the following is a fair example from WagbuUock 

 HiU, 410 feet above O.D. on Easthampstead Plain : — 



Large material. 



Subangular flints 73"8 % of weight. 



Plint-pebbles 221 



Chert 4-1 



Quartz „ 



Small material. 



41-9 o/o of weight. 

 35-7 „ ' 



13-4 



The gravels of the great plateau are in most cases roughly strati- 

 fied, and even where they are to all appearance without stratification 

 slight signs of bedding are often seen if one obtains a good section 

 through to the Bagshot Sand at a place where the gravel is thick. 

 It seems probable that Dr. Irving has made too much of the 

 question of stratification and contortion,^ for in the first place the 

 Glacial Gravels themselves are often beautifully stratified, and in 

 the second the example of unstratified gravel at Broadmoor which 

 Dr. Irving mentions ^ is not the only case. Thus there is a good 

 example of a mottled unstratified gravel at 360 feet above O.D., at 

 the southern end of Chobham Ridges, above Deep Cut Bridge. In 

 the large pit 405 feet above O.D., a mile west of Rapley Parm, the 

 upper part of the gravel is much contorted, and on Hartford Bridge 

 Plats, 325 to 333 feet above O.D., to which I now pass on, the 

 gravel is usually unstratified. 



These Plats are covered with a sheet of Southern Drift next in 

 importance to that of the great plateau. The diagram, fig. 1 (p. 31), 

 cuts through the eastern end, where the ridge is 325 feet above 

 O.D. or 37 feet lower than Crawley Hill, the nearest spur of the 

 great plateau, and numerous pits and sections occur all along the 

 Plats from 305 to 333 feet above O.D. They show gravel often 

 11 feet or more thick, usually mottled dark red and white, some- 

 what clayey, with very little sign of stratification except perhaps 



^ Op. cit, p. 561. ' Loc. cit. note. 



d2 



