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PROCEEDINGS COTTESWOLD CLUB 
1919 
of any traces of a moraine. The unloading of ballast from 
vessels in the Channel may lead to erroneous conclusions 
(66, p. 372). 
It has been considered probable that the former extension 
of high ground across the estuary at Sharpness or Aust formed 
the barrier of a Severn lake in which the gravels, sands and clays 
were laid down. So far as can be ascertained there is no 
Glacial Drift on the high banks bordering the Severn at either 
of those places. 
Such a barrier, whatever its nature, must have been in 
existence in mid-Pleistocene times, and, although the operation 
may have formed a part of the Tertiary erosion of the Severn 
Valley, it is improbable that a wide gap could have been 
excavated in hard rock, to a depth of about 150 feet, in the 
comparatively short time that has elapsed since the Glacial 
Drift was deposited. 
Some of the above-mentioned causes would obstruct the 
transport of debris to the sea, but, apart from the supposed 
existence of a ridge across the valley, they do not appear 
sufficient to raise the level of a Severn lake to the required 
height or otherwise to account for the phenomena. They would 
merely result in the formation of shoals and banks that may 
have held up small lakes occupying different positions as the 
floods shifted the debris. 
There is no record of the occurrence of Glacial erratics or 
other Drift material in large areas on the Severn Plain over 
which a lake of the required depth would have extended, 
and to which debris-laden ice-floes would have been carried 
far beyond the present limits of the gravels and sands of Glacial 
age. It has been argued that the ice-floes may have been kept 
near the centre of the lake by the current due to outflow, but 
such a condition must have been intermittent, and they would 
occasionally have been driven towards the shores of the lake 
by winds and currents. 
Glacial Drift and northern erratics of many varieties occur 
in gravels near Worcester up to heights of about 90 feet above 
the Severn, an elevation not excessive in relation to the shelly 
sands and gravels at 1,120 feet O.D. at Gloppa ; 1,250 feet at 
