254 UNDERGROUND WATSRS OF NORTH-WEST YORKSHIRE. 
thesi; Proceedings will be found an account of the Physical 
(geography and Geology of Ingleborough from the pen of Professor 
T. McKenny Hughes. To these works those readers who wish 
to make a detailed study of the same are referred. Other 
papers on the subject are mentioned in the Bibliography of 
the Yorkshire Caves hy Mr. S. W. Cuttriss, which follows this 
Report. 
In the following pages it is intended to give such an outhne 
of the geography and geology of the area as is necessary fcr 
the i^roper understanding of the work of the Committee on 
the circulation of the underground waters of the district. 
Ingleborough forms a bold hill 2,373 feet in height, and 
is an outlying spur of the Pennine Range. It is separated 
from its neighbours on the East by the Valley of the Ribble, 
from those on the south by that of the Wenning, and from 
Whernside on the west by Chapel-le-Dale. It forms therefore 
a roughly triangular patch of high ground separated from 
surrounding hills by deep valleys, and on this account was 
chosen as a suitable area for tlie investigation of the movements 
of underground water, inasmuch as these movements were 
unlikeh^ to be complicated by any flow of water from the neigh- 
bouring heights. 
The area is also suitable for an investigation such as the 
present, on account of tlie large number of streams which flow 
for some portion of their courses beneath the surface of the 
ground. Indeed, every stream which courses down the upper 
slopes of Ingleborough sooner or later sinks into the limestone 
which forms the base of the hill, to emerge in one of the sur- 
rounding valleys. 
On reference to the accompanying map and sections, 
PI. XXIII., and Figs. 1 and 2, it will be seen that the summit 
of the hill consists of Millstone Grit, resting upon a series of 
shales with thin limestones and grits (Yoredale Rocks), which in 
turn lie upon the great mass of the Mountain Limestone which 
is here 600 to 700 feet in thickness. At the base of this forma- 
tion is a great unconformity, and below this are highly folded 
and inclined rocks of Ordovician and Silurian age. 
