* 
84 PROFESSOR T. MCKENNY HUGHES, M.A. 
beast to inhabit. Sometimes, however, when all the hill is 
full after some great thunderstorm, water spurts out of every 
joint and spouts in torrents from each cave, and until the 
cave is quite beyond the chance of such catastrophes, we 
cannot hope to find a clear, continuous record of its old 
inhabitants. 
To give an example of a cave now being formed in one 
part and periodically modified in another, I will carry you to 
the flanks’ of Ingleborough, where the conditions are pecu- 
liarly well suited for the formation of caves and for the 
examination of all the accompanying phenomena. Many of 
you are familiar with the form of the grand bluff known as 
Ingleborough,—the most conspicuous feature as you look 
north from Lancashire towards the borders of Yorkshire and 
Westmoreland. Its flat cap of millstone grit ; its steep slopes 
of rapidly-crumbling Yoredale shale, here and there braced 
up by throughs of sandstone, or grit, or limestone; its great 
table of mountain limestone, on which these all stand; and 
its base of Cambrian and Silurian, altogether combine to 
furnish some of the most charming bits of scenery and most 
interesting bits of geology in the kingdom. On the 8.H. 
slopes of Ingleborough is a great hollow space where the 
water runs off the impervious Yoredale shale and the patchy 
drift down to the basement table of mountain limestone. 
The drainage area is about a square mile, and the stream is 
usually small and generally lost at once in the first open joints 
of the limestone that it gets to. But a flush of rain-water 
soon fills these crevices to overflowing, and the surplus water 
rushes on 100 yards or so to a great chasm, known as Gaping 
Gill Hole, into which it plunges with a roar. The air dragged 
down, tangled in the water, ascends in a current, carrying 
mist and spray far above the chasm’s brink. I have watched 
this wonderful abyss many a day of storm and sunshine. No 
one has ever been to the bottom of it; but I can tell you 
something more about it that bears directly on the subject 
we are considering. 
In that country, so favourable for the formation of all the 
various kinds of swallow-hole, cave, and keld, I once had the 
good fortune to witness one of those grand storms which in a 
few minutes change the face of nature, and in a few hours 
leave a mark that ages may not efface. 
I had climbed some way up Ingleborough. It was a 
glorious July morning. Myriads of insects were busy with their 
own various pursuits. ‘The haymakers were hard at work ; 
more hurried, perhaps, as the weatherwise saw thickenings 
towards the south, and felt the sultry heat that warned them 
