112 R. M. Deeley—The Thames Valley Gravels. 
the fluvio-glacial gravels; but the exact relationship of the deposits 
to the fluvio-glacial gravels is uncertain. It is about 28 miles from 
the eastern edge of the Map, Pl. LV, Fig. 1. 
The gravel at High Halston, 18 miles, is a deposit which is from 
100 to 200 feet high, and may belong to this series of gravels. ‘The 
highest outlier at the Telegraph Station, which is still more elevated, 
cannot belong to the series of gravels we are considering. 
Leigh, at 15 miles, shows gravel from about 150 to 160 feet Prera 
O-D.; “whilst the Southend ‘eravel is from 100 to 160 feet. From 
the neighbourhood of Southend the gravels run in the direction of Sales 
Point at the mouth of the Blackwater River. In this stretch the 
gravel of the main stream seems to have been joined by a fluvio- 
glacial fan coming from the direction of Billericay, where it is from 
220 to 240 feet above O.D. — Its distance from the fluvio-glacial gravel 
of the old Thames is about 16 miles, and allowing 5 feet per mile fall 
we get 14) to 160 feet as the height of the gravel of the main stream. 
Southminster stands on an outlier of gravel which varies from 
50 to 80 feet above O.D., and this place is opposite the point where 
the centre line of the old Thames Valley reaches the east side of the 
Map, Pl. IV, Fig. 1. 
All the gravels of the Tilehurst Terrace do not contain erratics 
derived from the glacial drifts: On the south side of the River 
Thames Bunter pebbles are absent, except towards the east. Portions 
of the gravel to the south and west were formed by the local drainage, 
whereas the portions to the north side of the river were largely 
formed by the drainage from the ice margin, the deposit becoming 
a more and more mixed one as it is followed to the east. 
The slope of the Tilehurst Terrace deposits from the Goring Gap 
to the east does not appear to have been by any means a regular one ; 
but whether the irregularity is wholly due to the varying amount of 
water and sediment coming down from the various ice lobes or to the 
subsequent warping of the district is not clear. Perhaps the debris 
was poured into the Thames Valley by the St. Albans Ice Lobe in 
such quantities that it collected here in unusual thickness in the 
neighbourhood of the confluence of the Colne and Thames. 
At Southend the High-level Terrace Gravels wrap the slopes. in 
avery peculiar manner. Indeed, it would appear that the present 
estuarine portion of the Thames ‘Valley in pre-Chalky Boulder-clay 
time continued to slope to lower levels in a north-easterly direction, 
and that in Chalky Boulder-clay time the valley was deeply filled with 
fluvio-glacial gravels which have since been re-excavated, leaving 
traces of the High-level Gravel Terrace deposits at all heights from 
sea-level up to 130 feet or more. 
This filling up of the valley with glacial detritus in its lower 
reaches may have been due to the ereat quantities of material thrown 
into the valley by the Lea Valley Lobe and the ice lobes which 
debouched into the valley from the rivers of Suffolk and. Essex. 
During the time the Chalky Boulder-clay was being laid down 
the Tertiary and Cretaceous rocks extended some distance in a north- 
easterly direction into the North Sea, being probably continuous with 
those of France. Since this time subaerial denudation and coast 
