Bone Caves. 459 



the north accompanied by Lions and Hyaenas, and when 

 the winter cold returned they retreated further south, 

 leaving such snowy land as there was in exclusive posses-, 

 sion of White Bears, Musk-sheep, Eeindeer, and perhaps 

 hairy Mammoths with a warm coat of wool beneath the 

 long hair. But with the advance of research inter- 

 glacial episodes began to be established, when, in the 

 language of Mr. James Greikie, there took place ' a great 

 recession of the confluent glaciers consequent upon a 

 change of climate.' l 



In connection with this subject it is now necessary 

 to say something of the bones found in limestone caves, 

 especially as the subject is intimately connected, not 

 only with a large and partially extinct mammalian 

 fauna, but also with the presence of man as a hunting 

 denizen of the British area, at the time in which these 

 carnivorous and browsing mammalia roamed the 

 country. 



Bone-caves are often of very old date, and always 

 occur in limestone strata, in which they have been 

 formed in consequence of part of the carbonate of 

 lime having been dissolved. Most solid limestone rocks 

 are jointed : that is to say, they are parted by narrow 

 fissures, often vertical, through which water that falls 

 on the surface can easily find its way. .Rain-water per- 

 colates through the joints, and the carbonic acid, 

 picked up by the water as it falls through the air, by 

 degrees dissolves part of the limestone, and carries it 

 away in solution in the form of bicarbonate of lime. 

 Eunning in underground channels, caves have thus been 

 formed, often of great extent, and branching in many 

 directions, through which streams sometimes still run. 2 



1 ' The Great Ice Age,' p. 339, second edition. 



2 The great limestone caves of Kentucky form the most pro- 



