114 THE LAPSE OF TIME. 



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, de- 

 pendent 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 simultane- 

 ously. 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 com- 

 mercial 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. 



But the cavern inscriptions make it as certain as 

 can be that the rate of speed here allowed for the 



