te of deposit allow about 5000 years for the date of
palaeolithic men; but Prestwich and others, on the basis of stalagmite
deposits, claim a vastly higher antiquity for the men who made the
implements found in Kent's Hole and Brixham.

If we now turn to these stalagmite floors, when we consider that they
have been formed by the slow solution of limestone by rain-water
charged with carbonic acid, and the dropping of this water on the
floor, and when we are told that in Kent's Cavern a marked date shows
that the stalagmite has grown at the rate of only one twentieth of an
inch since 1688, and that there are two beds of stalagmite, one of
which is in some places twelve feet thick, we are impressed with the
conviction of a vast antiquity. But when we are told by Dawkins that
the rate of deposit in Ingleborough Cave may be estimated at a quarter
of an inch per annum, and when we consider that the present rate of
deposit in Kent's Hole is probably very different from what it was in
the former condition of the country, stalagmite becomes a very unsafe
measure of time. With respect again to the accumulation of
kitchen-midden stuff in the course of the occupancy of caverns, this
proceeds with great rapidity, when caves are steadily occupied and it
is not the practice to cleanse out the debris of fires, food, and
bedding. Even when the occupation is temporary, a tribe of savages
engaged with the preparation of dried meat and pemmican in a very
short time produce a considerable heap of bones and other
rejectamenta.

Looking next to the extinction of animals, we find that the species
found in the oldest deposits containing human remains are in part
still extant. Others which are locally extinct we know existed in
Europe until historical times, that is, within the last two thousand
years. How long previously to this the others became extinct we have
no certain means of knowing, though it seems probable that they
disappeared gradually and successively. We have, however, farther to
bear in mind the possibility of cataclysms or climatal changes which
may have proved speedily fatal to many species over large areas. In
any case we have this certain fact that, though the time elapsed has
been sufficient for the extinction of many species, it does not seem
to have sufficed to effect any noteworthy change on those that
survived. Farther, we may consider that time is only one factor in
this matter, and not the one which is the efficient c