water percolating through the rock finds its way into the cave by the walls rather than the roof, we find stalagmite only, exhibiting its greatest thickness round the edges of the cave and cementing its contents into a breccia. This is the case with some of the caves of the Dordogne and the South of France, and does not seem of necessity to imply any great alteration in the physical conditions of the surrounding country since the caves were formed. It is also possible that the floors of the caves have, by being trodden, become more impervious to water than they originally were, and that a loose mass of porous bones upon them may, by conducing to evaporation, have caused a deposit of carbonate of lime from water which, had the caves remained unoccupied, might have run through or over the floors without forming such a deposit.
With the other class of long and tortuous caves we must, in nearly all cases, recognize, with Sir Charles Lyell,[1] three successive phases:—1st, the period of the dissolution of the rock to form the channel; 2nd, the time when the channel was traversed and enlarged by subterranean currents of water; and, 3rd, the period when these currents were diverted, and the cave became filled with air instead of water.
The rate of deposit of stalagmitic matter varies so much with different conditions, that its thickness affords no true criterion of the length of time during which it has accumulated. Under ordinary circumstances, however, a thickness of even a few inches requires a long period of years for its formation.
Having made these few preliminary remarks as to the formation of caverns and the deposits occurring in them, I proceed to notice some of their characteristics in connection with the relics of human workmanship found in the deposits, and in doing so cannot restrict myself to British caves, but must refer also to some of those on the Continent, which are more numerous, and have likewise furnished a more extensive and varied series of remains.
It had not escaped the attention of early authors, that in remote times specus erant pro domibus;[2] and, to use the words of Prometheus,[3] "men lived like little ants beneath the ground in the gloomy recesses of caves." It is, however, strange to find a Roman author recording the occurrence of worked flints in the caves of the Pyrenees; for if we accept the description of the ceraunia given
