JOWETT AND MUFF I GLACIATION OF BRADFORD, ETC. 207 
for four miles, gradually decreasing in altitude to 575 feet near 
Hawksworth. Along much of its course it has been dug into 
and turned over for the limestone boulders which it contained, 
but an almost undisturbed section can be seen on the north 
side of the reservoir, near Reva. Here it is formed of a sandy 
clay, containing numerous boulders of grit, limestone, and 
gannister scattered through it. The limestone boulders are 
usually rounded and striated, whilst those of grit and sandstone 
are sometimes quite angular and are seldom scratched. 
Although the material exposed in the above section might 
be called a boulder-clay, it is not a typical till. Other parts 
of the moraine are more gravelly, and the mounds have been 
compared to an esker by previous observers. The above section, 
however, shows that this drift ridge is not an esker. 
Two small drift mounds near Green Gates, on Ilkley Moor, 
connect Lanshaw Delves with the morainic mounds at the west 
end of the moor. 
The relation of the till to this moraine is of some interest. 
At Lanshaw Delves the moraine seems to mark the upper limit 
of the drift on the south side of Wharfedale. No boulder-clay 
or gravel has been found south of the moraine between it and 
the watershed, though there is nothing in the shape of the ground 
to prevent such accumulation. Shortly after crossing the 
watershed, where the altitude is less than 1,000 feet above O.D.,. 
boulder-clay occurs indifferently on both sides of the moraine. 
It will be seen from the contoured map that the broad transverse 
valley east of Rumbles Moor opens widely towards the upper part 
of Wharfedale, but its junction with Airedale is somewhat con- 
stricted and points down that dale. The till on its western 
slopes is arranged in long narrow drumlins with smooth rounded 
contours. They run obliquely down the slope of the ground 
in a south-easterly direction, but curve round towards the east 
at their lower ends. It is thus evident that the Wharfedale 
ice pushed into the transverse valley to beyond Guiseley. It 
reached a height of at least 700 feet on the hills east of Guiseley, 
where a curved morainic ridge concave towards the west runs 
from West Carlton in a south-easterly direction for three-quarters 
of a mile. The western edge of this lobe of ice was marked by 
