908 STRATIGRAPHICAL GEOLOGY. [Book VI. 
than 25 feet, is overlaid by a remarkable bed of clay, loam, and gravel 
(‘‘loess” or “‘trail”’), three feet or more in thickness, which in its con- 
torted bedding and large angular blocks probably bears witness to its 
having been accumulated during a time of floating ice. The strata 
below the glacial deposit have yielded a remarkable number of 
mammalian bones, among which have been found undoubted human 
implements of chipped flint. The number of species amounts to 26, 
which include Rhinoceros leptorhinus, R. tichorhinus, R. megarhinus, Hlephas 
antiquus, E. primigenius, Megaceros Hibernicus, Felis leo, Hyzna crocuta, 
Ursus ferox, U. arctos, Ovibos moschatus, Hippopotamus major, and present 
another example of the mingling of northern with southern, and of 
extinct with still hving forms, as well as of species which have long 
disappeared from Britain with others still indigenous. Other ancient 
alluvia, far above the present levels of the rivers, have likewise furnished 
similar evidence that man continued to be the contemporary in England 
of the northern rhinoceros and mammoth, the reindeer, grizzly bear, 
brown bear, Irish elk, hippopotamus, lion, and hyena. 
The caverns in the Devonian, Carboniferous, and Magnesian limestones 
of England have yielded abundant relics of the same prehistoric fauna, 
with associated traces of Paleolithic man. In some of these places the 
lowest deposit on the floor contains rude flint implements of the same 
type as those found in the oldest river-gravels, while others of a more 
finished kind occur in overlying deposits, whence the inference has been 
drawn that the caverns were first tenanted by a savage race of extreme 
rudeness, and afterwards by men who had made some advance in the 
arts of life. The association of bones shows that when man had for 
a time retired, some of these caves became hyzna-dens. Hyzna bones 
in great numbers have been found in them, with abundant gnawed bones 
of other animals on which the hyenas preyed. Holes in the limestone 
opening to the surface (sinks, swallow-holes) have likewise become 
receptacles for the remains of many generations of animals which fell 
into them by accident, or crawled into them to die. Ina fissure of the 
limestone near Castleton, Derbyshire, from a space measuring only 25 by 
18 feet, no fewer than 6800 bones, teeth, or fragments of bone were - 
obtained, chiefly bison and reindeer, with bears, wolves, foxes, and hares. 
France.—lIt was in the valley of the Somme, near Abbeville, that 
the first observations were made which led the way to the recognition of 
the high antiquity of man upon the earth. ‘That valley has been eroded 
out of the chalk, which rises to a height of from 200 to 300 feet above | 
the modern river. Along its sides, far above the present alluvial plain, 
are ancient terraces of gravel and loam, formed at a time when the river 
flowed at higher levels. ‘The lower terrace of gravel, with a covering of 
flood-loam, ranges from 20 to 40 feet thick, while the higher bed is about 
30 feet. Since their formation the Somme has eroded its channel down 
to its present bottom, and may have also diminished in volume, while 
the terraces have, during the interval, here and there suffered from 
denudation. Flint implements have been obtained from both terraces, 
and in great numbers, associated with bones of mammoth, rhinoceros, 
and other extinct mammals (p. 898). 
The caverns of the Dordogne and other regions in the south of France 
have yielded abundant and varied evidence of the coexistence of man 
* Boyd Dawkins, Karly Man in Britain, p. 188, 
