196 JOWETT AND MUFF I GLACIATION OF BRADFORD, ETC. 
they cannot be connected with, normal stream action. The 
ice-striae on the high hills indicate an ice-movement across 
the deep tributary valleys of the Aire. 
Mr. J. E. Wilson published in 1900 the results of an 
investigation undertaken to verify the statement by Prof. 
Carvill Lewis given above. He adduced evidence to show 
that there was a lake in the Bradford basin having its outlet 
at Laisterdyke. Streams flowed into this lake, via Stream 
Head Col and Chellow Dean ; the Leventhorpe beds were 
said to be the delta of the former stream, and the signific- 
ance of the fact that this delta was at the same altitude 
as the Laisterdyke outlet was pointed out. Chellow Dean 
and the gorge at Stream Head Col were regarded as the 
result of the overflow of a lake in the Worth and Harden 
drainage areas. The deep notch at Sugden End, near 
Haworth, w^as considered to be the outlet of the Worth 
Valley lake at one period.* 
Much of the following paper was presented by us as a 
brief summary to the Bradford Meeting of the British 
Association (1900).t 
II. — General View of the Surface Features of the Area. 
The portion of Airedale between Skipton and Leeds is 
excavated wholly in rocks of Carboniferous age. In the 
north-west, around Skipton, are to be found the rocks of 
the Carboniferous Limestone series. These are followed 
about a mile below Skipton by the Millstone Grits, the out- 
crop of which occupies the largest part of the area under 
description. In the south-east the Lower Coal Measures — 
overlying the Millstone Grits — extend from the hills east of 
Oxenhope to Cottingley, and thence along the southern side 
of Airedale to Kirkstall, beyond which they occupy both 
sides of the dale. Outliers of Lower Coal Measures on 
Millstone Grit occur between Yeadon and Horsforth, on 
Hope Hill, near Baildon, and at the head of the Glusburn 
* Brit. Assoc. Report (Bradford), 1900, p. 755. 
tBrit. Assoc. Report (Bradford), 1900, p. 756. 
