doubt, shelter; while the reason for the Danish kjökken-möddings occurring along the coasts is to be found in the fact, that the principal food of those who left these heaps of refuse, was derived from the sea.
In other instances, the tenancy of a cave by man seems to have alternated with that by bears, hyænas, or other predaceous animals; so that the relics left by the two classes of occupants have become more or less mixed, sometimes without the intervention of water, and sometimes by its aid. In such caves, it is commonly the case that the bones are imbedded in a red loamy matrix, to which the name of "cave-earth" has been given, and which appears to consist, in a great measure, of those portions of the limestone-rock that are insoluble in water charged with carbonic acid.[1] Such red loams are common not only in caves, but on the surface of many calcareous rocks, and would be liable to be brought into any place of resort of man or beast, adhering to the feet and skin, especially in wet weather; though some portion of what is found in the caves may be a kind of caput mortuum left in position after dissolution and removal of the calcareous rock; or it may be sediment deposited from turbid water.
Another important feature in caverns is the stalagmitic covering with which the bone deposit is so frequently sealed up or converted into a breccia. Like the stalactites on the ceiling, the stalagmite on the floor is a gradually-formed laminated deposit, composed of thin films of crystalline carbonate of lime, deposited from the water in which it was held in solution as a bicarbonate, by the escape of the excess of carbonic acid which rendered it soluble. I have already cited the action of rain-water falling on a surface of limestone covered with decaying vegetable matter as an agent in forming subterranean channels; but we have here, curiously enough, the reverse action produced of filling them up. For this to take place, contact with the air appears to be necessary; so that at the time when a cavern was completely filled with water, no calcareous spar would be deposited. If partially filled, though stalactites might be formed, stalagmite would not; and it is probably to some alternation of wet and dry conditions that several beds of alluvium[2] occasionally occur interstratified between successive layers of stalagmite. When, as occasionally happens, the
- ↑ See Rev. H. Eley, F.G.S., in Geol., vol. iv. p. 521. Pengelly, Geol., vol. v. p. 65.
- ↑ Lyell, "Princ. of Geol.," 10th edit., vol. ii. p. 520.
