QUATERNARY FAUNA OF GIBRALTAR. 55 
Prison, this plateau is about 400 feet above the sea; and it slopes gradually to the 
south at an angle of about 11°, so that at its southern boundary, which is in a 
vertical inland cliff about 100 feet high, its level above the sea is from 250 to 300 
feet. It is bounded on the east and west sides by nearly perpendicular cliffs, whose 
base is in a terrace about 100 feet above the sea-level. 
The southernmost division of the rock (d), termed Europa Flats, is also a tolerably 
even plain, which gradually slopes to an elevation of not more than 50 feet above the 
level of the water. The sea-bottom, where visible in calm weather at the base of the 
eastern cliffs of the Europa Plateau, and beyond the masonry with which its southern 
flank is covered, also constitutes a rocky plain, with precisely the same waterworn 
surface as that of the “ Windmill Hill” and Europa Plateau, and constituting, in fact, 
a third level or step. That part of this lower plain which was above water was formerly 
termed the Lower Europa ; but it is now entirely concealed by the military works. 
The eastern face of the rock is a nearly perpendicular precipice, being, in fact, the 
escarpment of the limestone strata. Upon this face, where they have not been removed 
by denudation or weathering, a succession of sea-worn terraces, one above the other, at 
distances of about 100 to 150 feet, may be observed up to a height of 800 or 900 feet, 
apparently indicating so many successive stages of elevation. ‘The western face forms 
an irregular slope, interrupted by longitudinal cliffs and ravines, and gradually shelving 
at the bottom into a gentle declivity, partly ¢a/ws, upon which the town is chiefly built. 
With the exception of some ferruginous sands and shales on the western flank, the 
mass of the Rock of Gibraltar consists of hard grey Jurassic limestone. Wherever 
the surface is sufficiently exposed the rock is seen to be traversed throughout by innu- 
merable ramifying fissures, which occasionally widen out into extensive caverns, either 
partially empty or, as was formerly seen at Rosia Bay, completely filled with ossi- 
ferous breccia. 
The principal reason of this fractured condition is undoubtedly to be sought in the 
circumstance that the strata have been subjected to very great disturbances. They 
have, in fact, been twisted, as it were, in different directions. This is shown very plainly 
by the fact that the angle of the dip varies very much in different parts—to such an 
extent, indeed, that its direction is reversed at the opposite extremities of the pro- 
montory. ‘These changes, moreover, are very abrupt; and the points at which they 
take place seem to correspond with the two lines of fracture termed ‘ Quebradas” 
(a, b, fig. 1, p. 54), and with the line of passage from the elevated to the lower portion of 
the rock (¢). And it is precisely at or near these lines of fracture that the principal 
known caves and fissures are situated. 
But, besides the movements by which the strata have been thus affected, Mr. Smith 
is of opinion, and has pretty conclusively shown, that the whole mass of the rock has 
been elevated and depressed more than once to the extent of its entire height, even 
“since the testaceous fauna was the same as at present.” 
12 
