54 
rises but a few feet above the level of 
the bay, has at one time been covered 
by the sea; leaving the Rock of Gibral- 
tar an abrupt rocky island mass a few 
miles from the main land of Spain. 
‘The north and east sides of this rock 
present an almost perpendicular steep- 
ness from top to bottom. ‘The west 
side slopes at about an average angle 
of 45°. The south end or side of the 
rock is at first quite perpendicular, 
and then falls gradually down towards 
Europa Point. The townis built near 
the foot of the west side of the rock. 
The length of the rock from north to 
south may be about 2} miles ; its 
breadth from west to cast. from half a 
wile to above a mile; and its height 
about 1000 feet above the level of the 
sea. The top of the rock is a long nav- 
row ridge, running north and south, 
the west side sloping down to the town 
and bay; the cast side, from its rugged, 
perpendicular front, almost inducing 
the opinion, that Gibraltar Rock, as it 
now exists, is only the half of a large 
hill, the cast side of which, in some 
great convulsion of nature, has been 
torn asunder from the other, and pre- 
eipitated info the Mediterranean, 
The view from the top of the Rock of 
Gibraltar, the Mount Calpe of old, in a 
clear day, is most magnificent. 'To 
the east, the Mediterranean stretches 
out before us as far as the eye ean 
reach; and on either side its lofty 
shores, the mountainous coast of Africa 
on the one hand, and, on the other, the 
more beautiful, perhaps, but scarcely 
less hilly coast of Kurope, both gradu- 
ally receding from cach other, to form, 
as it were, a broader basin for the 
Mediterranean; the village of St. 
Roch, to the north, beautifully situated 
on the top of a gently sloping hill; the 
Bay of Gibraltar, and town of Alge- 
ziras to the west, and to the south the 
sister pillar, the lofty Mount Abyla, 
and her neighbouring mountains. 
The Rock of Gibraltar is composed 
of limestone, of which there are two 
principal varictics, one forming the 
great mass of the hill, hard, fine- 
grained, with a splintery or conchoidal 
fracture, possessing considerable lus- 
tre, and generally of a light-grey co- 
Jour, sometimes also dark, sometimes 
nearly white, and in one part of the hill, 
where it is quarried as a marble, oc- 
curring beautifully variegated. This 
limestone is stratified, and near the top 
of the hill, as is well seen, the strata run 
fyom nearly north-east to south-west, 
Proceedings of Public Societies. 
_ [Atg. 1, 
and inclining to the south-west at an 
angle of 60° or 70°. The other princi- 
pal variety is a conglomerate or brec- 
ciated limestone, formed of the debris 
of the former, connected by a red cal- 
carcous basis, and wrapping round the 
other centra} mass. This conglomerate 
variety appears to be still forming on 
the hill. Besides these, there occur 
two beds of a flinty slate rock, both 
very much decayed, and one of them 
containing numerous round and angu- 
lar pieces of limestone. ‘These beds 
appeared to be contained in the older 
solid limestone, and to run in strata 
conformable to it. 
At the foot of the hill, the sole rock 
visible is the conglomerate limestone, 
which oceurs in great abundance, and 
forming smal! hills. The imbedded 
masses are often of a very large size. 
The basis is a red, coarse, caleareous 
cement, or a calcareous tuff, more 
or less hard, and often intermixed 
with round coneretions of calcareous 
sinter. At the foot of the hill the 
rock is often almost entirely composed 
of this calcareous tuff. As weascend 
the hill, this conglomerate rock de- 
creases in quantity, the imbedded 
masses become smailer, and the con- 
necting basis less abundant, more com- 
pact, finer, and of a lighter colour. 
The imbedded masses, which are of 
every shape, are undoubtedly broken 
porti:.ns of ihe solid limestone nucleus. 
When we have ascended above two- 
thirds of the hill, this conglomerate en- 
crusts the interior mass to the depth 
only of a few inches, and a little 
higher up almost entirely disappears, 
when the solid limestone forms the 
whole upper part of the hill. 
That such is the structure of Gibral- 
tar Rock, a ceiitral mass of old and 
solid limestone, covered to various 
depths by a newly formed conglo- 
merate, such as has been deseribed, 
appears, from the examination of those 
parts of the hill through which roads 
have been cut in the rock, of those 
long arches cut through both the con- 
glomerate and solid limestone, and in 
particular of those amazing excava- 
tions, as they are called, planted with 
cannon, ofien running to a great ex- 
tent, and parallel to the exteriorsurface 
of the hill, from which they extend into 
the rock from twenty to fifty feet, cutting 
in various places through the “conglo- 
merate into the solid mass. Partly 
owing to the darkness in these long 
arches, and from other circumstances, 
1 seldom 
