PLEISTOCENE CAVE-DEPOSITS. 83 



short of it, while the intervening drier periods might well have 

 experienced a rainfall not much greater than that of the present. 

 Thus it is evident that the present rate of stalagmitic accretion 

 in Kent's Cavern cannot he safely relied upon as a standard by 

 which to judge of the time required for the formation of the old 

 pavements, underneath which the Pleistocene cave-earths he 

 huried. The question of age, as we see, is not so easily settled, 

 for we have to take into account the effects produced by previous 

 climatic conditions ; and as we can form only a more or less 

 uncertain estimate of these effects, it is impossible that our con- 

 clusions can be other than vaguely approximative. Even on the 

 most extravagant assumption, however, as to the former rate of 

 stalagmitic accretion, we shall yet be compelled to admit a period 

 of many thousands of years for the formation of the stalagmitic 

 pavements in Kent's Cavern. 



There is another consideration, however, which must not be 

 forgotten when we are endeavouring to form some adequate 

 conception of the time required for the accretion of such stalag- 

 mitic pavements. We have no reason to suppose that their 

 growth has always been continuous ; on the contrary, we know 

 very well that in many cases the accretion on the floors has fre- 

 quently been interrupted. Sometimes the caves were filled, 

 or partially filled, with water, and their former occupants ex- 

 pelled for prolonged periods, during which no growth of stalag- 

 mite could take place. At other times, when the caverns were 

 the frequent resort of large predatory animals like the bear, such 

 pellicles of stalagmitic matter as formed upon the floor would 

 often be trampled on and commingled with earth and clay, which 

 might be readily removed when, now and again, flood-waters 

 found access to the caves, so that any particular bed of stalag- 

 mite can seldom or never represent the entire quantity of car- 

 bonate of lime that dropped in solution upon the floor from the 

 time when the stalagmitic pavement first began to accrete. 



This is clearly indicated by the structure of the stalagmitic 

 pavements themselves. Sometimes these are remarkably pure 

 and homogeneous, indicating a prolonged and perhaps continuous 



