Page:The Zoologist, 3rd series, vol 1 (1877).djvu/148

122 present. During the subsequent glacial epoch the whole of the British islands, including portions since submerged, were clothed in an eternal winter mantle, partly snow and partly in the form of glaciers, which moved down from the high to the low lands, carrying with them rocks and débris of all kinds to form fresh deposits.

The remains of the animals in question have been preserved chiefly in caves or in river deposits. The limestone caverns, in which they are found, usually present the following appearances:—On the floor there is a bed of calcareous drippings hardened into a substance known as stalagmite. Under the latter may be seen successive layers of clay and stalagmite of various thickness. Sometimes the osseous remains are found on the floor of the rock simply embedded in the stalagmite. The various levels formed by an alternation of cave-earth or clay and drippings may represent various stages in the history of a cave. For instance, on the surface flint tools, fashioned by man, together with bones of the Red Deer and Oxen, may be found; in the second layer may be discovered the remains of herbivorous quadrupeds and of Lions and Elephants, the larger bones showing evident traces of having been gnawed by predaceous animals. Under those conditions, it may be surmised that the cave was originally a den of carnivorous animals, which had dragged in the bones of their prey, until the surface, getting gradually covered over by stalagmitic drippings, became eventually the resort of man. Of course the absence of traces of his presence is no proof that he may not have been contemporary with the lions in the second deposit; at the same time, we are not justified in admitting his presence unless we find the bones of domestic animals, flint tools, or other relics of man mingled in the same stratum. As to the age of these two deposits, they may or may not represent long periods; much depends on the rapidity or otherwise of the influx of the cave-earth, either through rock-fissures or by the aid of streams, which convey large quantities of soil into underground caverns; whilst the extent of dripping of the lime-water from the roof and sides, and its hardening, depend entirely on circumstances; for a cave may get filled to the top in a comparatively short time, or its filling may be the work of ages. In either case some covering of the bones must take place before they have time to decay, as they otherwise would do if left uncovered. It is wonderful how little stalagmite is required to preserve a bone; a mere crust, not