310 THE BEDSHIEL KATMS 



imposed upon so large an area of North-western Europe, 

 began to disturb the state of equilibrium of the Earth's 

 crust. It is thought by many that if there is a removal 

 of any considerable mass from a part of the Earth's surface, 

 that part will b^gin slowly to rise ; and that, if there be 

 placed any additional load upon it, it will begin to sink. 



By this means it is possible that the Grlacial Period may 

 have worked out its own end. The heavy load of ice 

 remaining on the land, instead of quickly flowing off as 

 rivers do, brought about a slow depression, which ended by 

 carrying the land down about one hundred and fifty feet 

 lower than its present level. The mountain summits were 

 gradually lowered by the depression. Rain fell where 

 previously nothing but snow had been precipitated. The 

 glaciers were cut off at their source, and, in consequence, 

 the ice gradually began to melt away as it stood, without 

 retracing its steps. As it melted away, the rocks, stones, 

 mud, and sand (including any organisms that had become 

 enveloped within the ice) were gradually left behind as a 

 sediment, which forms our well-known Till or Boulder Clay. 



The materials liberated at the surface of the ice, after 

 being much rolled and washed by the super- glacial streams, 

 began by degrees to be washed down into crevasses. As 

 these widened with the melting of the ice, channels were 

 formed, which eventually deepened until they extended right 

 to the bottom of the ice. By these channels the rolled, 

 washed, and water- worn materials which had been brought 

 together, often from all quarters, and had been at one stage 

 incorporated within the ice, were gradually heaped up, layer 

 upon layer, into ridges and mounds, until the enclosing 

 walls of ice finally melted away, and Eskers were the result. 



This explanation of the origin of Eskers or Kaims, which 

 is now very generally accepted, enables us to account readily 

 for many phenomena, which, on the hypothesis that they 

 were of marine origin, seemed totally inexplicable. Such are, 

 the fact that Eskers are very commonly moulded over pre- 

 existent mounds of rock ; and that they often include a few 

 well glaciated stones, as well as others which glacial strise 

 have been more or less completely obliterated by the rolling 

 and wear they experienced on the surface of the glacier, 



