242 
presence of these in many of the holes now described, clearly 
shows that both appearances are of somewhat ancient date. 
Had these been produced by artificial means, too, we should 
in all probability have found some trace of what had been 
dug out. Some have supposed that water has been the agent, 
and that these cavities were made in what once formed the 
bed of some majestic river or torrent. These boulders, hurried 
round in the whirl of the water, are thought to be the stand- 
ing proofs of the process having taken place. If so, we 
should probably find traces of the action of water, if not 
at least one such pebble in each cavity. No such traces are 
now visible. Others, ^ain^contend for vol canic agency ,_a nd 
that when the mass of ^Jimj!stojQe..wa.s jn_a_fluid or a plastic 
state, a jet of gas must have forced its way through^ and 
that these are consequently the mouths of so many extinct 
volcanoes. So far as could be ascertained, however, by 
digging down into several until we came to the solid rock, no 
such means has been at work ; at least no trace of fire is 
visible on the texture of the stone ; and had they been caused 
by any such force from beneath, whether a jet of steam or 
gas, some traces, either in the shape of lines or grooves in 
the sides, or of masses of ejected refuse lying round, would 
surely be visible. 
But one supposition, then, seems left ; and this, perhaps, 
the most likely of all : — that owing to the roof of certain 
natural hollows at some depth in the earth having fallen in, 
the ground above has gradually settled down to fill up the 
void. The shape, and the entire absence of mounds of 
refuse — for it is quite flat all round — seem to confirm this. 
This, however, it will be seen, only gets rid of one set of 
hollows by substituting another, by no means a particularly 
philosophical mode of explaining away a difficulty. One 
other rather singular formation drew my attention, as some- 
what connected with these holes, or at least very near them. 
