The usual mode of accounting for the bone-breccias so eommonly found in caverns open to the day can scarcely be considered by any body as quite satisfactory. It seems usually taken for granted that that mixture of sand, clay, small stones, and fragments of bone must necessarily have been brought there by streams of water, or washed in by waves. And yet in many instances—perhaps in by far the great majority of instances—nothing can be imagined as much less likely to have happened than the aggregation of such materials by any means of that kind: that it should have been an occurrence of almost universal prevalence may well be deemed impossible. For under what circumstance can it be conceived that floods of water, in every region where open caverns exist in the rocks, should have picked up a heterogeneous collection of bones just in time to lay them quietly down again in every hole into which the muddy stream could gain access? For we must really suppose so well-timed an acquisition of future fossils, before we can admit the usually received hypothesis of the manner in which they were deposited where we find them; since no one can suppose that the whole of the solid matter borne along by any great flood—not to say by every such flood—could have been such as we observe so constantly in these bone-breccias.