164 CAVES AND CAVE DEPOSITS. 
examine the contents to see whether in their character or arrange- 
ment they indicated the action of the in-rushing water, or 
whether they are such as could never have survived the scour of 
tidal and wind-driven waves. When we have to enquire into 
the origin of caves in inland cliffs and on mountain-sides, now 
far above the sea, where many of the traces above-described 
have been long removed by denudation, there are further tests 
to be applied. There we should have regard to their manner of 
occurrence and their place in the physical geography of the 
neighbourhood. A sea-cave does not necessarily, or even com- 
monly occur in the line of drainage from the uplands, but in 
the higher cliffs and headlands between the valleys that run 
down to the sea. Whereas the caves due to subterranean water- 
courses lie in the lines of drainage ; and the caves due to sub- 
aérial waste coincide in distribution with the outcrop of the beds 
that readily lend themselves to that kind of weathering. 
Moreover, allowing for the possibility of unequal elevation of 
different parts of a coast-line, we can still generally find sufficient 
evidence to show whether the rock in which the cave occurs 
forms part of an old sea-cliff or of an escarpment. 
We must remember also that during the formation of a sea- 
cave the base of the cliff is being swept by the sea. Sometimes 
an inland stream washes the base of a rock in which a water- 
course cave has its outfall, but generally in the case of inland- 
formed caves a vast mass of talus is being formed along the 
base of the cliff in which the cave occurs The scour of floods 
through the cave may keep the mouth open, but as the water. is 
being drained off to other and lower levels, this sweeping of the 
cave mouth ceases, and the cave deposits show interbedded fallen 
rock and transported earth and stones, and often the remains of 
animals. 
As a general statement we may say that a typical sea-cave 
runs into a cliff which rises vertically from the level of the floor 
of the cave, or is even undercut a little, because the talus has 
always been removed from the base, so that the fragments break 
away all over the face of the cliff from top to bottom, and the 
base sometimes is even undermined by the waves. 
In the case of an inland cliff, on the contrary, the fallen rock 
is not removed, so that only the upper part of the cliff above 
the sloping mass of talus is exposed to the action of the weather. 
The exposed part is reduced in height as the talus grows, so 
that the cliff keeps on receding above only, as the talus keeps 
covering up more and more of the lower part. 
Of course, the sea-cliff, when removed inland by elevation, 
gets, after a time, eaten back by subaérial weathering, and 
covered over by talus like any ordinary escarpment. 
Gaping fissures of such a character that they could in any 
case be looked upon as caves are very rare, but the fault-breccia 
