272 
HUGHES : IXGLEBOROUGH. 
side of the great slab of limestone, and it is lifted out and hurled 
along. I have sometimes seen in Dent, after a flood, a great 
slab left, here and there, on end at the down-stream side of the 
joint-bounded cavity from which it had been lifted out. 
These manifeste.tions are of especial value to the ever in- 
creasing band of spelseologists who are doing so much to elucidate 
the formation of caves and the course of underground waters 
in cavernous rocks. If we see an ordinary spate lifting a slab 
four feet square out of a cavity one foot deep — say 1,000 lbs. 
weight of rock — what must be the effect of the water in Gaping 
Gill w^hich would have a dead weight of 10 atmospheres when 
the chasm was full and an intermittent thud due to the velocity 
proper to the depth as the water was subsiding in it ? 
As might be expected from the character, condition, and 
lie of the Mountain Limestone in this district, the phenomena 
connected with its springs are very varied and interesting. 
The rock is traversed by joints and faults which are opened out 
first by chemical action of the water holding carbonic and other 
acids in solution, and then by its mechanical action as it carries 
along boulders and grit and mud. A network of caves is thus 
formed along the fissures, and when there has been an exception- 
ally heavy rainfall the lower outfalls are unable to carry off the 
surplus water, which then finds its way out through old deserted 
channels at higher levels. But the outcome of it all is that the 
flood occasionally rises in the creviced rock and produces a head 
of water, w^hich comes out through the small openings at the 
base or on the sides of the rock under enormous pressure. But 
in some cases the water does not come to the surface directly 
from the fissures in the limestone, but finds its way into permeable 
strata wiiich abut against it, as, for instance, where a limestone 
talus or a bed of gravel lies at the base of a limestone cliff. The 
springs in such a case are thrown out w^here the permeable 
strata end, and, if a wash from Boulder Clay, or the clayey 
residuum from decomposed limestone overlaps the permeable 
strata, the water may burst out anywhere. 
In Jenkin Beck, east of Ingleton, some very curious springs 
are thus produced. Here a fault throws dow^n shales belonging 
to the Yoredale Series against the Mountain Limestone. A stony 
