Vol. 50.] 



PLEISTOCENE DEPOSITS AT TWICKENHAM. 



453 



29. On the Geology of the Pleistocene Deposits in the Valley of 

 the Thames at Twickenham, with Contributions to the Fauna 

 and Flora of the Period. By J. R. Leeson, M.D., F.L.S., 

 F.G.S., and G. B. Laefan, Esq., B.Sc, E.G.S. (Read April 

 25th, 1894.) 



In June 1892 excavations were begun for the construction of an 

 effluent culvert from the Twickenham Sewage Works to the River 

 Thames. The work was commenced at the foreshore of the river, 

 near the celebrated Pope's Grotto. The Thames is a tidal river at 

 that point, with a difference of about 8 feet between high and low 

 water : the low-water line is 5 feet above Ordnance datum. The 

 excavations commenced at low-water level on the Middlesex bank 

 of the river, and were continued in a north-westerly direction, with 

 an incline of 1 in 500, through certain roads and lands towards the 

 Sewage Works. The length of the section was about one mile, and 

 the width of the cutting was 4 feet 6 inches. The sloping bank 

 between the river and the Kingston main road consisted of soft, 

 loose material, which had evidently been deposited there in modern 

 times. After crossing under the main road, distant about 60 yards 



Fig. 1. — Plan showing the 'position of the sewer-cutting in the 

 Valley of the Thames at Twickenham. 



From 

 Staines. 



from the river, the excavation, which at this point was about 10 feet 

 deep, entered into the reddish-yellow gravels which abound in this 

 neighbourhood. It was then continued for some distance through 

 these gravels under a roadway called Pope's Grove, at ( depths 

 varying from 12 to 19 feet. A considerable quantity of water was 

 found in the excavation, and had to be pumped. Beneath the 

 gravels was the London Clay, which was met with in the excavation 

 at two points, and in one place was penetrated to a depth of 5 feet. 

 After leaving the London Clay the excavation was continued 

 through gravel alone for a short distance, and then a dark loamy 



