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POPULAR SCIENCE REVIEW. 
the indications of littoral action, there is scarcely an exposed 
portion of the limestone of Gibraltar, from the sea level up 
to the highest point of the rock, that does not present proofs 
of marine erosion ; and perhaps in few localities is this more 
evident than on the plateau of Windmill Hill, rendered famous 
by the wonderful discoveries of Captain Brome. Here, on 
the surface, and running into the great tortuous rents which 
intersect the rock in every direction, may be observed innu- 
merable caldron, trough-shaped, or circular hollows, smooth 
and rounded, and perfectly distinct from the withering and 
honeycombing, the result of atmospheric and chemical decom- 
position now going on. Caves are also plentiful; but the 
differences between a vaulted chamber formed by the sea 
waves, and a fissure with its roof partially or entirely covered 
in by calcareous infiltrations, or fragments of rock jammed 
between the opposing sides, and brought about by movements 
consequent on upheaval or depression, are so very various that 
in many instances what at first sight might appear to be a 
cave, will turn out subsequently to be a covered-in fissure. 
It is only when the cavity opens horizontally without the roof 
communicating with the surface, whereby the deposits or 
organic remains might have been conveyed thereinto, that we 
opine should the name cave or cavern be applied. Openings 
of this description are common on the sea face of the rock of 
Gibraltar. In one, situated on the scarped face of a cliff at 
Europa Point, Captain Brome found several flint implements 
and pieces of charcoal embedded in the red soil and calcareous 
deposits on its floor. The celebrated pithecoid human skull, 
discovered many years since, is said to have been found in a 
cave of this description on the north front of the rock. But 
one of the most important and valuable discoveries made by 
the above-named indefatigable geologist, was that of many 
human skeletons. Captain Brome's attention was directed to 
a small hole on the plateau of Windmill Hill, into which his 
terrier was often in the habit of entering in quest of rabbits. 
On opening this out, an irregular- shaped rock cavity was dis- 
covered, filled almost to the roof with calcareous incrustations 
and soil. It measured a few feet in height, by eight or ten 
in breadth. In a crevice close to the entrance lay the skele- 
tons of several human beings, dispersed about seemingly 
without any order. The skulls were well formed, and did not 
indicate any very great antiquity. Associated with the human 
bones were flint hatchets and knives, well polished, besides 
a metal hook, charcoal querns, and edible marine shells. Slabs 
of a light reddish-brown sandstone formed the hand-mills just 
mentioned, or were polished on one or more sides, as if they 
had been also used for sharpening the flint tools. This rock 
