e limestone plateau, 1158 ft.
high, which forms the divide between the waters flowing into the Mersey
on the west and the Humber on the east. Both swallow-hole and cave were
completely blocked up with debris, and the latter was filled with red
and yellow clay, horizontally stratified and containing pebbles of
sandstone from the neighbouring ridge of Axe Edge, and bones and teeth
of fossil mammals, some waterworn and others without traces of transport
by water. All the mammals belong to well-known species found in the
Pliocene strata of East Anglia, and in Auvergne and Italy. Among them
were the sabre-toothed lion (_Machairodus crenatidens_), the hyena of
Auvergne, the mastodon, and the southern elephant (_E. meridionalis_),
and rhinoceros (_R. Etruscus_), and Steno's horse. Most of the bones had
evidently been gnawed by hyenas and accumulated in one of their dens,
and had afterwards been carried by water into the chambers deep down in
the rock, where they were found. Since that time the general level of
the district has been lowered by denudation to an extent of more than
230 ft., and all the hyena dens destroyed with the Pliocene surface not
only in this district but generally over the world. In this case a
covering of limestone some 270 ft. thick, including the depth from the
present surface, protected the remains from the denuding forces.

_The Pleistocene Caves._--The search after _ebur fossile_ or unicorns'
horn, or in other words the fossil bones which ranked high in the
_materia medica_ of the 16th and 17th centuries, led to the discovery of
the ossiferous caverns of the Harz Mountains, and of Hungary and
Franconia. The famous cave of Gailenreuth in the last of these districts
was explored by Goldfuss in 1810. The bones of the hyena, lion, wolf,
fox and stag, which it contained, were identified by Baron Cuvier, and
some of the skulls have been proved by Busk to belong to the grizzly
bear. They were associated with the bones of the reindeer, horse and
bison, as well as with those of the great cave bear. These discoveries
were of very great interest, because they established the fact that the
above animals had lived in Germany in ancient times. The first bone cave
systematically explored in England was one at Oreston near Plymouth in
1816, which proved that an extinct species of rhinoceros (_R.
leptorhinus_) lived in that district. Four years later the famous hyena
den at Kirkdale in Yorkshire was explored by Buckla