88 PROFESSOR T. MCKENNY HUGHES, M.A. 
As we cannot follow these watercourses down from above 
through all their subterranean wanderings, let us go down 
into the valley below where the water comes down, and see if 
we can work our way back into the hill towards the foot of 
the great chasm, and see what is going on there. It is here 
we find what is more properly a cave being formed. The 
water drops from one level to another, then runs along 
between the beds, and drops again. By putting your ear to 
the fissured rock in one place, you can hear, from the deep 
recesses of the earth, the sound of a waterfall that man has 
never seen. Not far off, a beautiful clear river flows out of 
the lower cave. This is 600 feet below the swallow-hole, 
where the water enters on the hill above. When the rain 
floods the stream above, this, too, runs turbid. Some 20 feet 
above it is the entrance to the other cave, the celebrated 
Ingleborough Cave, a more ancient outfall for the water, 
which now runs at the lower level. 
This cave was explored many years ago by Mr. James 
Farrer. I have followed it for about a quarter of a mile, and, 
with some others, been let down to a lower level at the end. 
We squeezed our way along till we came to a long, deep cave, 
full of water, which seemed to flow gently towards the mouth 
of the lower cave. In the great flood of 1872, all the sub- 
terranean caves and fissures were filled, and the water spouted 
out of the upper cave, carrying along with it great masses of 
rock, which helped to break up the stalagmitic floors and 
barriers. This flood was so exceptional that most of the 
débris was carried clean away ; but we saw, when we examined 
the ground round the mouth of the cave, and the well-known 
passages inside, what had been going on; how stalagmitic 
floors had been undermined, broken up, and re-deposited, and 
how the torrent débris was sometimes left in the embayed 
corners of a limestone cave. But this was a cave not far 
above the existing watercourse. When a cave has been 
formed in the side of a rapidly-deepened gorge, where, how- 
ever high the flood may rise, the water can never sweep it 
out with a rush, gentler processes of denudation and depo- 
sition still go on. ‘The débris that falls about the mouth 
ponds back the rain, and gathers in the fissured rock, and 
turns in the rivulet that would have trickled down the hill. 
The damp clay clings to the rock and frets away its surface, 
and things washed in work their way down along the face 
of the opening, gradually-weathered limestone, and lie in clay 
washed down with them. 
It is easy to distinguish the chemically-fretted rock from 
that which has been worn, smoothed, and rounded by the 
