THE ROYAL ARTILLERY INSTITUTION. 
297 
Fossils in 
coarser kind 
of minute 
shell breccia. 
in it. It is one of the most important geological deposits, and consists of 
pieces of limestone besides fragments of small shells; these shells are both 
so small, and so waterworn and fractured as to defy identification, but I 
have lately obtained some perfect fossils in it from a similar 
though much coarser conglomerate in the “ galleries; " it 
bears considerable resemblance to millstone grit, and having 
in some places a red tinge from the presence of oxide of iron. 
It is very tough and hard, although the coarser kind is liable to 
crumble when continually wetted. It is used to a great extent for lining 
the embrasures, and attains a thickness in some places of nearly 300 ft.; 
somewhat beyond Martin's Cave it exists at a height of nearly 650 ft. 
Mussels have been found, also, in a fissure, by Mr Smith, at a 
3xu height of 34 ft.! above the sea level, perfectly preserved. This 
careful observer to some extent unravels the clue to the history of the 
numerous deposits, which he ascribes to the broken, and dislocated condition 
of the fundamental limestone rock, which bears the appearance of com-, 
parative recent disturbance so frequently repeated, and of such magnitude 
as to exceed that of any other European locality. 
Besides the coarser kind of shell breccia (specimen No. 4) obtained from 
the galleries, there abounds also a kind of pudding stone (see 
Pudding stone, specimen No. 10) and a great variety of limestone formations 
thereabouts; masses of calc-spar are found mostly more or less 
imperfect in their crystalline form, the most perfect mass I obtained (is 
specimen No. 7 in the case) near Poca Boca Cave. 
The limestone generally is a compact rock varying in colour 
Limestone of from a dark ash grey and snake colour (see specimens No. 3), 
variable colour. ^ near ]y w hite (see specimen No. 2), it is intersected throughout 
by ramified caves or vertical fissures, the angle of stratification 
varying at different parts, and reversed at the opposite extremities of the 
promontory, as well as in two or three places along the crest of the hill 
downwards. The greatest varieties of colour in the limestone I find to exist 
at Bosia, from whence Nos. 2 and 3 specimens are taken, as well as the 
greatest variety of breccia (see specimen No. 6 from Bosia). 
Near to Forbes' Barrier was found, about the same time as 
Human skull, the bones of the ox, deer, &c. a skull which was in possession 
of the Geological Society of Gibraltar, and afterwards presented 
by them to the Museum of the Soldiers' Home; considerable doubts were 
at one time entertained as to the nature of the skull, but upon the dis¬ 
memberment of the museum, being believed to be a human one of low 
organization, it was sent to the celebrated anatomist Professor Busk, F.B.S., 
who pronounced it to be undoubtedly that of a human being of the lowest 
known organization somewhat analogous to the “ neanderthal," his opinion 
being at the same time supported by the late lamented Dr Falconer, Y.P.B.S., 
and several other scientific men, and when, early in October, 1864, ex¬ 
amining with Professor Busk the slope of the old quarry of Forbes we found 
the matrix in which we believed the skull had been imbedded, which was 
a raised beach of about 100 ft. above the sea level, and which was seen 
everywhere to be cropping out of the limestone slope, the inner portion of 
the beach being covered with broken pieces of calcareous rock, and the 
outer being broken off, disjointed masses being carried down by the 
