INTRODUCTORY. 7 



The melting away of the lower part of a glacier gives 

 rise also to several other characteristic phenomena. Where 

 the foot of a glacier chances to be on comparatively level 

 land, the terminal moraine often covers a great extent of 

 ice, and protects it from melting for an indefinite period 

 of time. When the ice finally melts away and removes the 

 support from the overlying morainic debris, this settles 

 down in a very irregular manner, leaving enclosed depres- 

 sions to which there is no natural outlet. These depres- 

 sions, from their resemblance to a familiar domestic uten- 

 sil, are technically known as kettle- holes. The terminal 

 moraines of ancient glaciers may often be traced by the 

 relative abundance of these kettle-holes. 



The streams of water arising both from the rainfall 

 and from the melting of the ice also produce a peculiar 

 effect about the foot of an extensive glacier. Sometimes 

 these streams cut long, open channels near the end of the 

 glacier, and sweep into it vast quantities of morainic mate- 

 rial, which is pushed along by the torrential current, and, 

 after being abraded, rolled, and sorted, is deposited in a 

 delta about its mouth, or left stranded in long lines be- 

 tween the ice- walls which have determined its course. At 

 other times the stream has disappeared far back in the 

 glacier, and plunged into a crevasse (technically called a 

 moulin), whence it flows onwards as a subglacial stream. 

 But in this case the deposits might closely resemble those 

 of the previous description. In both cases, when the ice 

 has finally melted away, peculiar ridge-like deposits of 

 sorted material remain, to mark the temporary line of 

 drainage. These exist abundantly in most regions which 

 have been covered with glacial ice, and are referred to in 

 Scotland as kames, in Ireland as eskers, and in Sweden as 

 osars. In this volume we shall call them hames, and the 

 deltas spread out in front of them will be referred to as 

 kame-plains. 



With this preliminary description of glacial phenome- 



