CAVES AND FISSURES. 
71 
not so firmly as in the Gibraltar breccia, and in much of that which 
occurs in the caves of Germany: portions of bone and single frag¬ 
ments of rock are also found occasionally incased with a thin crust or 
coating of the same substance; but, generally speaking, it is not suf¬ 
ficiently abundant to hold the mud and bones together in a solid 
mass after they are moved from the cave. In some few spots there 
were balls of iron stone, and concretions of ochre formed in the clay; 
in others there was a considerable deposit of manganese ore dispersed 
through the sand and porous portions of the loam; in the latter were 
also concentric balls of the same ore inclosed within each other after 
the manner of the ochreous aetites # . 
It was in one of these oblique apertures in the present face of the 
rock at Oreston, and at about forty feet above the bottom of the 
quarry, that the congeries of bones, skulls, horns, and teeth I am now 
about to speak of, was discovered. Mr. Whitby had collected 
fifteen large maund baskets full of them before our arrival; these 
have been sent to the College of Surgeons, and distributed to 
various public collections. In the upper parts of the cavity from 
* A small quantity of manganese is found disposed in a similar manner in some 
parts of the sediment in the cave at Kirkdale; and I have often found this ore incrusting 
the pebbles and sand in subordinate beds of a large mass of mixed diluvial gravel, e. g. 
in Lord Barrington’s gravel pit at Sedgefield, in the county of Durham; and in some 
gravel pits near Liege. It does not pervade the entire mass, but is usually limited to 
beds of a few inches in thickness, and seldom spreads in these beyond a few feet in 
breadth. The source from which it has been derived in situations of this kind is by 
no means obvious; it is decidedly of later origin than the gravel itself, and seems 
analogous to the incrustations of iron and carbonate of lime, which are often disposed 
in a similar manner around the component materials of common surface gravel, cementing 
it into a solid breccia, (e. g. in the gravel pits immediately on the east and north of Ox¬ 
ford). It seems to have been deposited from water infiltrated through the gravel and 
sand which are thus incrusted by it. 
