56 MR: G. BUSK ON THE ANCIENT OR 
This brief geological notice will suffice to account for the innumerable caverns and 
fissures by which the Rock of Gibraltar is penetrated in all parts from its summit to 
the base, and whence it has occasionally been termed the “ Hill of Caves.” 
From a general survey of the conditions under which the osseous remains occur, all 
the phenomena may be explained, as was remarked by Major Imrie, on the supposition 
that they were washed into the more or less vertical open cavities by the heavy 
autumnal floods. In support of this it may also be stated that most of the bones, more 
especially at the articular surfaces, are sun-cracked, or have that peculiar kind of reti- 
culated fissuring which arises from exposure to atmospheric agency. Others, again, are 
simply crushed, the splinters being recemented by a fine, ochreous, crystalline stalagmite. 
This condition can only be accounted for on the supposition (in the absence of tooth- 
marks) that the bones had either fallen from a considerable height or, what is more 
probable, had been broken by the falling upon them of heavy portions of rock after 
they had become lodged in the fissure. To this mode of introduction must be added 
the circumstance, now for the first time made known, that in all probability the entire 
bodies of animals, either before or after death, were occasionally precipitated into the 
gaping cracks. Instances of this will appear in the sequel. 
With respect to mineral condition, many of the fossil bones are heavy, dense, hard, 
and strongly infiltrated with manganese; whilst others, though deprived to an equal 
extent of the animal substance, which is replaced in some measure by carbonate of 
lime, are perfectly white, easily cut or powdered, and without any trace of manganese’. 
Notwithstanding the abundant evidence of the existence of the Hyena as a former 
member of the Rock-fauna, not a single bone has as yet been detected bearing indu- 
bitable marks of its teeth. The only bones showing marks of gnawing (by Arvicola, 
or perhaps the Fox) belonged wholly to the upper compartments of the Genista Cave ; 
and they are either human or of species coexistent with man. 
As regards the amount and nature of its osseous constituents, the breccia differs very 
much in different parts of the rock and at different elevations. In fissures near the 
base the breccia contains usually but few bones, being chiefly formed of angular frag- 
ments of the grey limestone imbedded in the universal ochreous indurated matrix; in 
other places the extraneous contents are almost entirely land shells (/elix, Bulimus 
decollatus, &c.); whilst in the more elevated and precipitous points of the mountain 
the narrow fissures are filled with a breccia consisting almost entirely of the bones of 
birds and other small animals, no doubt conveyed by the Hawks which there find their 
habitation and breeding-places. 
In most parts the fissures appear to have remained open until they were filled with 
‘ Small fragments of bone, usually, if not wholly, of Cervus or Jbea, and deeply carbonized, were met with 
eyen in the deepest part of the Genista Cavern. These fragments, probably representing the relics of human 
repasts, have doubtless found their way through small fissures in the floor or sides of the upper chamber. They 
are never coated with stalagmite. 
