The fact being admitted, the question is. How is it to be ac- counted for ? This juxtaposition is no certain proof of contempora- neoiisness. These caverns, once the resort of wild beasts, became to men places of concealment, of defence, of worship, or of sepul- ture, and, therefore, as Sir Charles Lyell himself admits, " It is not on the evidence of such intermixtures that we ought readily to admit either the high antiquity of the human race, or the recent date of certain lost species of quadrupeds." ^
In immediate connection with the passage just referred to, Lyell suggests another method by which the remains of animals belong- ing to very different ages of the world might become mixed to- gether. That is, " open fissures " which " serve as natural pit- falls." He quotes the following account from Professor Sedgwick of a chasm of enormous but unknown depth, which " is surrounded by grassy shelving banks, and many animals, tempted toward its brink, have fallen down and perished in it. The approach of cattle is now prevented by a strong lofty wall ; but there can be no doubt that, during the last two or three thousand years, great masses of bony breccia must have accumulated in the lower parts of the great fissure, which probably descends through the whole thickness of the scar-limestone to the depth of perhaps five or six hundred feet." To this Lyell adds, " When any of these natural pit-falls happen to communicate with lines of subterranean caverns, the bones, earth, and breccia may sink by their own weiffht, or be washed into the vaults below." ^
1 Principles of Geology, ninth edition, p. 740. a Jbid. pp. 740, 741.