208 JOWETT AND MUFF : GLACIATION OF BRADFORD, ETC. 
the moraine, which stretched from Lanshaw Delves to Hawks- 
worth. The Wharfedale ice thus overtopped the Aire-Wharfe 
divide north of Hawksworth, where it sinks below the 1,000 
foot contour, and laid down its moraine along the slope of one 
of the tributary valleys of the Aire. This unexpected result 
shows that the Airedale glacier had begun to retreat whilst 
the Wharfedale ice was still at or near its maximum extension. 
The presence of the relatively high ground of Bingley Moor 
and Hope Hill, situated immediately to the west, must have 
assisted in fending off the Airedale ice from the Hawksworth 
ridge. 
IV. — The Striated Rock-Surfaces. 
The striated rock-surfaces, which have been found in this 
district, are with one exception on beds of grit. A thick bed 
of gannister provides the other example. Only the hard, com- 
pact rocks are capable of being well striated ; the soft rocks, and 
the surfaces of hard rocks with many cracks in them, are simply 
ploughed up and smashed by the passage over them of a mass 
of ice containing stones. A section was observed at Stone Hall 
Hill, Eccleshill, where beds of shaley sandstone were covered 
by boulder-clay 9 feet thick. The upper surface of the sandstone 
w^as smashed, and the layers were pulled over in the direction of 
ice movement, viz., towards the E.S.E. Boulders and clay 
were forced into the crevices of the shattered sandstone. The 
soft nature of some, and the rubbly nature of other of the rocks 
of the Millstone Grit and Coal Measure series has thus led to 
a comparative scarcity of striated surfaces. 
Striae have generally been found in places where the rock 
is now, or has been until recently, covered with boulder-cla}'. 
The action of the weather soon obliterates any scratches which 
may exist on exposed surfaces of sandstone and felspathic grits. 
Most of the striated surfaces are irregular. The consistent 
smoothing of the northerly or north-westerly facing sides of 
any prominences, whilst the south-easterly sides are left jagged 
and rough, affords the clearest evidence of a general ice move- 
ment from north-west to south-east. 
It will be noticed that where the striated surfaces occur 
high up on the sides or on the tops of the hills, the direction 
