264 
HUGHES : INGLEBOROUGH. 
reach the Mountain Limestone and begin to barrow into its 
depths by joint chemical and mechanical action ? 
Many other very interesting geographical features, dependent 
upon the structure of the rock, can be observed in this area. 
The scars upon the Fell side, however they may have originated 
in far off ages, have been cut back to their present position 
by the action of ordinary sub-aerial denudation, including 
under that a good deal of rough work during the glacial episode. 
But the long cafion-like valleys wdth precipitous sides seem to 
be directly due to other causes. If we follow up Clapdale, for 
instance, we pass Ingleborough Cave on our left and see how 
easily the wide flab roof might break and let down the rocks 
above. Still more likely does it seem that the broader roof of 
the cave out of which the water now issues at a lower level 
should some day give way. Higher up the valley we find on 
our left, just before we reacli Trowgill, a small gorge cut back 
into the hill, the upper or far end of which is full of broken lime- 
stone between which burrowdng animals, such as badgers, foxes, 
and rabbits, have found access to the cavernous limestone 
behind. Water no longer flows out here except in great storms, 
when every joint and fissure of the limestone is full. This is 
obviously being cut back by the weathering of the limestone 
exposed in the gorge and above the cave. Immediately beyond 
this we come to Trowgill, which is a narrow gorge with precipitous 
sides in the upper part, but opening out into steep turf-covered 
slopes lower down. (Plates XXX. and XXXI, ) Here we seem to 
have the mouth of a cave cut back, with the precipices broken 
down and rounded in the part which has been longest exposed. 
The floor of the ravine rises rapidly and the limestone closes 
across its upper end, showing that it is not an ordinary valley cut 
back by surface waterfalls and rapids. In the upper part, just 
before we get into the narrow passage through which we climb out 
on to the Fell, there are great horizontal openings between the 
beds like those seen lower down Clapdale. This gorge also looks 
like a cave cut back from its mouth. When we get out of the 
gorge we find ourselves in a narrow steep-sided valle}^ and, 
following it up, we see that its course is marked by swaUow 
holes, such as that known as Bar Pot, just over the Fell boundary 
