HUGHES : IXGLEBOROUGH. 
179 
through the cave has eaten its way do-wn through softer schist 
and left the hard beds of sandstone vertical on either side, 
as described by Playfair. 
There are many examples along this j^art of the valley of 
caves formed in this way, namely by the water, which has found 
its way down along joints to the very base of the Mountain 
Limestone, eating out channels in the underlying schists, and 
forming caves in the schist as well as in the limestone (see Fig. 2). 
Fig. 2. 
CAVE IX SCHISTS UNDER, MOUNTAIN LIMESTONE, BELOW RAVENSCAR, 
EAST SIDE OF CHAPEL-LE-DALE. 
Playfair goes on to say, " At the spot just described no 
breccia appeared to be interposed between the primitive and 
secondary rock ; but we found a breccia at another point of 
the same junction not far distant. This was at a cascade in 
the River Greata, called Thornton Force, about two miles and 
a half from the place just mentioned. The Greata here j)re- 
cipitates itself from a horizontal rock of limestone, and, after 
a fall of about 18 or 20 feet, is received into a basin which it has 
worked out in the primary schistus. This schistus is in beds 
almost perpendicular ; it exactly resembles that which has just 
been described, and stretches nearly in the same direction. 
On the south side of the river a breccia was seen lying upon the 
