436 cuTTRiss : notes ox the caves of yokkshikk. 
what there are are usually very impure. Some of the caves 
may be traversed for a quarter of a mile or more, but thev 
generally terminate, as far as it is possible to explore them, in 
one of three ways. Firstly, a deep pool with smooth vertical 
walls converging to a fissure only a few inches wide, the water 
showing no perceptible flow, and more or less covered with scum. 
Secondly, if the passage is in the direction of the dip of the 
rock it will broaden out and the flat roof descend to the surface 
of the water, or meet the loose stones which choke the channel. 
Faulting may, no doubt, in some cases be responsible for these 
obstructions ; in other cases they occur when the channel passes 
from one bed of rock to a lower. In this latter case, if an 
opening can be cleai'ed sufficiently large to squeeze through, the 
channel will open out again and may form a Cave of Debouchure. 
The third manner in which these caves terminate is by ending 
abruptly in the side of a Pot-hole. Great care should be observed 
in exploring Caves of Engulphment, owing to the possibility of 
a sudden rush of water and the danger of falling down holes 
which are easily unobserved in the darkness ; for this reason the 
leader of the party should always be roped. 
Caves of Debouchure far exceed the others in number. The 
entrance, with few exceptions, is either at the base of a limestone 
scar or at the upper end of a narrow gorge. It is generally 
commodious, with a broad flat roof, forming the underside of 
a bed of rock. A thin parting of softer material separates this 
from the underlying rock in which the water channel is cut. 
The softer rock is frequently eaten away for some distance on 
both sides of the channel, leaving the roof unsupported over 
a large area. In the caves on the east side of Ribblesdale the 
entrance passage rapidly shallows and creeping becomes necessary. 
This inconvenient attitude is not, however, necessary for long, 
as a vertical cross fissure will usually be reached, 20 feet or 
more in height. A cascade or waterfall will then have to be 
negotiated, beyond which the passage becomes a simple water- 
worn channel, gradually shallowing and broadening until it becomes 
too low to permit of further progress. An exception is found in 
