202 JOWETT AND MUFF : GLACIATION OF BRADFORD, ETC. 
watershed on either side of the dale. As might be expected, 
it is then weathered completely through to a yellowish or, where 
beneath the peat, to a greyish colour. 
Shales, particularly those of the Coal Measures in a driftless 
area, often weather at the surface to a fine yellow clay, which 
is to be distinguished from the weathered boulder-clay. The 
former may be seen passing down into rotten shale. It is of 
a buttery consistency when wet, is not gritty to the touch, and, 
if it contains any stones, these are quite angular and local in 
origin. 
ii. — SANDS AND GRAVELS. 
The stratified sands and gravels, though covering a much 
smaller area than the boulder-clay, are locally developed in 
thick masses. They attain their greatest development in the 
mounds and terrace-like features of the main valley. Isolated 
mounds and patches also occur on the hills, and water-worn 
gravels form fan-shaped accumulations at the mouths of some 
of the dry valleys which will be described below. Current- 
bedding is observable in almost every section. The pebbles of 
the gravels are derived from the same rocks as the boulders in 
the boulder-clay, and the general distribution of the various 
kinds is similar. The pebbles are generally well-rounded and 
water-worn. The sands and gravels usually overlie the boulder- 
clay, but are sometimes found to underlie or interdigitate with 
that deposit. There is, however, no persistent " middle sand 
and gravel " separating a lower from an upper boulder-clay, 
such as has been recognised in other areas. 
iii. — GRAVELLY OR CLAYEY DRIFT MORE OR LESS INTERMEDIATE 
IN STRUCTURE BETWEEN i. AND ii. 
A third kind of drift, intimately associated with the boulder- 
clay and the glacial gravels, consists of a confused mass of 
boulders and stones with a sandy or clayey matrix, which varies 
in amount from point to point. It is not always easily separated 
from either the gravels or the boulder-clay, and in fact it seems 
to pass in different sections into both these deposits. The 
stones are of similar kinds to those found in the boulder-clay. 
They are subangular or rounded, and are very variable in size, 
