642 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [June 22, 
In 1846, Prof. E. Forbes published the names of certain shells he 
had found in the Lancashire drift, amongst others a Dentaliwim from 
Preston*. 
In 1862, Mr. Hull? described the results of the mapping of 600 
square miles of drift around Manchester, which necessitated a modi- 
fication of Mr. Binney’s classification, a Boulder-clay resting on the 
upper sand and gravel, and the lower sand and gravel being often 
absent. 
RECENT.......... Valley-gravels and River-terraces. 
Upper Till, or Boulder-clay. 
Middle Sand and Gravel. 
{ia Till, or Boulder-clay. 
Form oF THE GROUND IN WeEsTERN LANCASHIRE AND CHESHIRE. 
Undulating plains (of Triassic and Upper Carboniferous rocks), 
more or less covered with glacial drift, cecupy the country between 
Liverpool and Chorley, westward of which a low plain covered with 
peat-moss borders the sea-coast. 
Between Chorley and Lancaster the rock surface is extremely low, 
often, indeed, beneath the sea-level; but beds of glacial drift, often 
150 feet in thickness, are piled up on it, forming a slightly inclined 
plane, dipping from the Pendle range towards the sea, where it 
forms a line of cliffs near Blackpool from 40 to 80 feet in height. 
This drift plain has been cut through, to a greater or less extent, by 
various brooks, streams, and rivers. Few, however, have reached 
the rock surface beneath, the Ribble and its tributary the Darwen 
being almost the only exceptions. 
The third area into which Western Lancashire and Cheshire may 
be divided consists of three extremely low tracts, in which not only 
the rock surface, as in the Preston district, hes below high-water 
mark, but in which the glacial drifts themselves have been denuded 
away, so that the sea has to be kept out by sea-walls and banks, 
and is daily making encroachments. They are all areas of former 
obstructed, and present artificial drainage, and are deeply covered 
with peat-moss, which reaches in one instance a thickness of 50 feet. 
The first district is the low country between Lancaster and Fleet- 
wood, lying on both sides of the river Wyre; the second stretches 
from the river Alt, north of Liverpool, to the river Douglas, north 
of Southport; and the third lies between the rivers Dee and 
Mersey, in that part of Cheshire known as the peninsula of Wirral. 
It is traversed by a small stream, called the Birket, falling into 
Wallasey Poolt, a tributary of the Mersey, and bounded to the south 
by an escarpment hereafter to be described. 
* Mem. Geol. Survey, vol. i. 
t Trans. Man. Lit. & Phil. Soe. vol. ii. (3rd series), p. 451. _Mem. Geol. Sur., 
Country around Oldham, 1864. 
¢ Pool, in this district, is synonymous with “brook; thus Bromborough 
Pool, Liverpool, Blackpool. 
