CAVES AND CAVE DEPOSITS. 163 
of the rock,” is frequently mentioned in the history of the wars 
of the fourteenth and fifteenth centuries. And the Aquitani, 
when pressed by Czsar’s troops, retreated to their caves in 
South-central France. I have heard of a man who lived for 
some time in a cave in Yorkshire, coming out at night for food ; 
milk from the neighbours’ cows, eggs, or whatever else he could 
lay hands on. I found many odds and ends in that cave which 
might have been relics of his sojourn, as well as others of more 
remote antiquity. 
There are hardly any records of research in caves which are 
known to have been occupied in recent or historic times. A 
systematic examination of all the caves in which history tells us 
the inhabitants of any district once took refuge, and an exact 
description of everything observed in them, would be very 
interesting, and might furnish important evidence bearing upon 
doubtful questions. 
Artificial caves, however, or artificially modified caves, form 
a very small proportion of those with which we have chiefly to 
do. The caves in which primeval man lived, and into which in 
old times hyenas dragged carcasses of the animals they killed or 
found dead along the river-courses, were all natural caves. So 
are the celebrated stalactite caves of Germany and America. 
We must enquire into the mode of formation of natural caves if 
we would understand the conditions which surrounded primeval 
man or speculate on his age. 
‘There are sea-caves formed by the waves that lash the cliffs 
as if sounding them to find theit weaker places. The water 
itself would soon destroy a jointed rock. As each storm-wave 
rolls in, it deals a tremendous blow on the fissured mass. very 
thin packing of clay between contiguous blocks is soon washed 
out, and the fissures themselves enlarged. Then there comes 
into play another action. ‘lhe space behind the block is filled 
with water; the thumping wave falls on the narrow opening on 
one side of it; the pressure is communicated to the body of 
water behind it, and the force being multiplied ten or a hundred 
times by the hydrostatic paradox, the block is hammered out. 
It is clear that such waves and such boulders as we are 
familiar with on the coast of North Wales would make short 
work of broken rock or rotten dyke, and any old cave or fissure 
opened out by the sea would not be likely to have much of the 
original deposits left in it. The first storm would clear out all 
earth and bones, and leave in its place only the well-worn 
pebbles of a rocky shore. By its form and by its contents we 
could generally make out whether it was a sea-cave or not. We 
should examine the rock to see whether the parts where the cave 
expands are those on which the sea would act with greatest force 
and efficiency, or whether the shape could be better explained 
by reference to torrents coming in the other way. We should 
