R. M. Deeley—The Thames Valley Gravels. EG 
north and north-west would sweep up these materials and produce 
a confused mass known as Clay-with-Flints”. But from the 
distribution of the boulder-clay and gravels the ice appears to have 
come from the north-east. Deep snow on the Chilterns may have 
modified the deposit. The Clay-with-Flints seems to be such a 
deposit as we may expect to find filling up surface channels formed 
by the subsidence of the chalk into underground channels resulting 
from the solvent action of water, or filling swallow-holes. As the 
Tertiary beds were removed they would supply material to fill up 
such hollows as they formed. The brick-earths thus produced rest 
upon a layer of clay and flints which seems to be a chalk residue. 
Sarsen-stones were once very probably distributed over the whole 
area, and where they rested upon the surface they were removed for 
building purposes centuries ago, or destroyed by atmospheric agencies. 
They are now only to be found where they were buried. 
At Sonning, Smith & Dewey’ give the height of the Boyn Terrace 
as 180 feet, and with this deposit they correlate the Dartford and 
Swanscombe Terraces. As the Tilehurst Terrace is at a height of 
275 feet at Sonning, the Boyn Terrace? is thus 95 feet lower. Both 
at Dartford and Swanscombe the gravels lie well within the limits of 
the Tilehurst Terrace Gravels. They must, therefore, have been 
formed either before the Tilehurst Gravels were laid down or whilst 
the River Thames was re-excavating its valley through the fluvio- 
glacial deposits. 
Very few remains have been found in gravels on a level with the 
Tilehurst Terrace Gravels except to the south of the Thames on the 
east and west sides of the Darent River. Here at Dartford and 
Swanscombe mammalian and other remains have been found in 
considerable numbers. Much further work will have to be done 
before the age of these mammaliferous gravels can be said to have 
been settled. The remains they contain seem to show that there is 
a wide gap between them and the Taplow or Middle Terrace deposits. 
On this point Hinton® says, ‘‘ Excepting the elephant, rhinoceros, 
Felis, and possibly two of the deer, all the forms mentioned. differ 
from those whose remains are found in the earliest deposits of the 
next or Middle Terrace of the Thames Valley at Grays, and they 
approach those occurring in the ‘ Forest Bed’ series and the Upper 
Val d’Arno Pliocene.” It is possible that the Dartford and 
Swanscombe Gravels are in part, at least, older than the fluvio-glacial 
gravels, for Leach * found in the lower portion of the Dartford Heath 
Gravel mammalian remains of beasts which it is unlikely lived when 
the upper portion of the gravel bed was deposited by a river fed by 
streams coming from an adjacent ice margin. 
1} Arche@ologia, vol. xiv, p. 178. 
2 The Geology of the Country around Windsor and Chertsey (Mem. Geol. 
Surv.), p. 67. 
3 Proc. Geol. Assoc., vol. xxi, p. 492, 1909-10. 
4 Proc. Geol. Assoc., vol. xxiv, p. 340. 
