three floors of stalagmite could have been formed in succession, and two of them successively broken up. They must have been formed, not during the whole of the period, but only during that part of it which _followed_ the introduction into Britain of wild beasts, and of men who used flint weapons; for one unmistakeable weapon of human manufacture, and innumerable bones of the great old cave bear have been found within the rock-like breccia of stone and stalagmite and cave-earth, some feet below both the floors of more recent formation[55]. The longer the period, therefore, we allow for the migration from the East and the dying out of civilized life, the shorter is the period left for the stalagmitic formation. Yet probably the whole twenty-three centuries would not suffice for the formation of one of the floors; how much less could a fraction of the period suffice to form all three, and to supply the intervals during which, through some change of circumstances, the cave-earth was accumulating, and consequently no solid floor being formed. At Matlock the drip is continuous, being supplied by a stream, and not being, as in Kent’s cavern, dependent on the chances of the rainfall and the quantity of water that may percolate through a limestone roof. At Matlock, for purposes of trade, it is an object that a coating of stalagmite should be formed as quickly as possible. With this view the water is allowed to fall at the rate of fifty or sixty drops a minute, the drip being maintained at numerous points simultaneously. At Matlock we may roughly estimate that an inch of stalagmite would require four years for its formation, so that twelve feet and a half would require six hundred years. In Kent’s cavern, on the other hand, the drip is often interrupted. There is no commercial interest at hand to regulate the speed in the most advantageous manner, so that it falls sometimes too quickly and sometimes too slowly. The points at which it falls are few and far between. It cannot reasonably be supposed in any year to produce even a twentieth of the effect we have estimated for the drip at Matlock. In other words, the two later floors of the cavern would alone require a period of twelve thousand years for their formation. Even at this rate the cavern would probably have been so extremely damp and uncomfortable that no men or beasts would have chosen it for a shelter in rainy weather.