HUGHES : IXGLEBOROUGH. 
141 
down from the crags round Ingleborough upon the long, straight 
valleys of Kingsdale, Chapel-le-dale, and Ribblesdale, which are 
easier of explanation. These three valleys represent three stages 
in the history of the cutting back of valleys into a mountain 
mass. The Carboniferous rocks dip gently in a northerly direc- 
tion, so that the rim of Mountain Limestone is higher and 
higher the further south we trace it. If, then, anything 
should sweep the surface of the Mountain Limestone, or of any 
one and the same bed in it, quite bare, the water would accu- 
mulate on it, deepening to the north, until a gorge was cut back 
from the rim to tap it. 
Thus we find in Kingsdale an alluvial flat on one of the 
lower horizons of the limestone, and the water cutting a little 
gorge through the rim at Thornton Force (Plate XXIII.), and so 
eating its way back to tap the valley above. In the case of this 
great jointed limestone the water does not all wait till it reaches 
the fall, but, working down into the cracks and opening them out 
by chemical and mechanical action, often carries all the water 
away through the crevices so formed, while the water tumbles 
over the top of the rock only when, after heavy rain, there is 
more than the subterranean channels can carry. At the north 
end of Chapel-le-dale, where the valley changes its character and 
the limestone is much covered by imper\'ious drift, this action is 
very striking. The greater part of the water of the stream is 
generally lost in a grand chasm known as Weathercote Cave, and 
only in very heavy floods fills this to the brim, and overflowing 
runs on through the surface channel. The water that disappears 
in the gravel at the bottom of Weathercote Cave boils out below 
in Jingling Pot and Hurtle Pot, and supplies the stream that 
runs down Chapel-le-dale. 
On the floor of Kingsdale there is Mountain Limestone. In 
Chapel-le-dale, however, denudation has removed all the lime- 
stone, and the valley lies on Silurian and Bala, and perhaps some 
older rocks. The basement bed of the Carboniferous is seen some 
way up the hill on either side. But as the rim of the Mountain 
Limestone arrested denudation and let the stream wind about 
B 
