204 JOWETT AND MUFF : GLACIATION OF BRADFORD, ETC. 
to the north of the town consist partly of gravel and partly 
of boulder- clay. The sections exposed in the widening of the 
railway line from the pointsman's box near the Parish Church 
to the Skipton road bridge showed hard blue boulder-clay passing 
upwards into yellow clay. Pebbles and boulders of limestone, 
generally striated, are abundant in the blue clay, but do not 
occur in the top three feet of the yellow clay. The hollows 
between the cuttings are floored with peat, which was over 
five feet thick, and contained remains of the oak near its upper 
surface. The cutting to the north-west of the bridge exposed 
a very stony blue clay passing upwards into yellow clay. The 
widening of the cutting below Marley Hall showed current- 
bedded sand and loam lying upon and banked around a mass- 
of coarse gravel. 
It has been suggested* that the terraces which lie on the 
flanks of the valley above Bingley may have been formed in 
a lake caused by the obstruction of the valley by the Bingley 
moraine. The altitude of the terrace is about 295 feet above 
O.D. 
The Nab Wood and Bingley moraines are almost connected 
by a line of gravel mounds, along which the railway runs. Recent 
excavations have exposed 35 feet of coarse gravel without 
reaching the base of the deposit. The gravel consists of pebbles, 
of Carboniferous grit, sandstone, and limestone, with a small 
admixture of Silurian grits, generally embedded in a matrix of 
sharp sand. The current-bedding generally dips to the 
east, whilst flat pebbles are tilted up so as to dip to 
the west, showing that the current of water which deposited 
the gravel came from the latter direction. At the sides of the 
mounds the bedding often conforms to the slope of the surface. 
The gravel ridge in many points resembles an esker, and it was 
probably formed by a sub-glacial stream of water in a tunnel 
in the glacier, perhaps at the time when the Nab Wood moraine 
was being accumulated. 
A shorter but serpentine gravel ridge situated on the north 
side of the canal bank, between Shipley and Saltaire, may have 
had a similar origin. A pit opened in the middle of the mound 
♦ Geology of Yorkshire Coalfield, p. 783. 
