OF NORFOLK AND SUFFOLK. 
I2 3 
THE GLACIAL SANDS AND GRAVELS. 
The advance of an ice-sheet must have been attended, 
especially in the earlier part of its course, by considerable 
erosion, with a corresponding deposition elsewhere of the 
eroded material, on the one hand as unstratified till or 
morainic gravel, or the other as deposits stratified by the 
flood water which issued from the ice when advancing or 
retreating. In the former case such beds would underlie, 
in the other they would overlie, the unstratified bottom 
moraine or till. 
The Westleton Beds. 
The North Sea Drift in its uncontorted form, to the south 
of the terminal moraine of the Cromer ridge, is generally 
underlain by pebbly and sandy gravel, the Westleton Shingle 
of the late Sir Jos. Prestwich, the stones being water-worn 
and rounded ; this shingle may be traced, in my opinion 
more or less continuously, as far south as Westleton. It 
was correlated, by him, but I think on insufficient evidence, 
with a number of isolated patches of gravel, extending into 
the counties of Herts, Bucks, Berks, and Oxon. Such 
gravels generally rest on high land, however, at elevations 
which gradually rise westward to 600 ft. O.D. 
The sketch map (fig. 6) shows the distribution of the beds 
which I regard as Westleton Shingle ; they are usually found 
in association with the Lower Glacial deposits. In places, 
as in the cliff section at Lowestoft, similar pebbly gravel 
occurs in the sands (Middle Glacial of Wood) which underlie 
the Chalky boulder- clay. In such case they may have been 
derived, I suggest, from the destruction of beds of Westleton 
Shingle, formerly existing in that neighbourhood. 
The Westleton gravels have been variously grouped with 
the Crag and with the Glacial beds. In places, however, 
they have cut into or eroded the Crag sands, as at Tharston 
Furze Hill, and near Norwich, while in the neighbourhood 
of that city they are overlain conformably by the Sprowston 
and Catton brickearth (North Sea Drift). I am therefore 
