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farther out, in the middle, and finally in its turn forms the surface, 

 becomes converted once again into water, sinks into a crevasse, 

 freezes again at a lower level, and takes its place amongst other ice 

 that will go through the same cycle of change. 



Whatever be the true explanation, there can be no doubt about 

 the fact that the bottom strata of ice near the head of a glacier 

 tend to become its top layers farther out. And with the upflowing 

 of the ice, substances entombed in the ice tend to work up to the 

 surface also. Their rate of ascent is proportionate to the difference 

 between their rate of descent through the ice under the action of 

 gravity (a factor not of much importance in such a case) and the 

 rate of ascent of the ice wherein they are entombed, under the 

 combined action of ablation and turgescence just referred to. The 

 nett result is a movement upwards ; and most important this factor 

 becomes in relation to the distribution of boulders, as James 

 Geikie has shewn in the paper referred to. We can readily under- 

 stand how certain boulders from the low grounds of Edenside 

 have been transported up hill a thousand feet or more within a 

 distance of five or six miles. How are we to explain such facts by 

 any theory of submergence? 



One result of the differential movements of the ice must have 

 been to bring together over any given spot, boulders that had 

 originally entered the main stream at many different levels, and 

 that had been derived from sources situated, in some cases, at 

 almost every point of the compass in relation to that particular 

 spot. It is quite conceivable that the different platforms of the 

 ice sheet around Penrith, for example, where its maximum thick- 

 ness must have exceeded two thousand feet, may have consisted 

 of ice that had originated, some in the Lake District, some in 

 Galloway, some around Cross Fell, and some near Stainmoor, 

 entering the seething mass from all points of the compass, and 

 at every level up to the highest limit of the ice. Under the 

 circumstances one can understand how at the climax of the Glacial 

 Period, the ice around Penrith may have had, dispersed throughout 

 its mass, detritus of all the rocks occurring in the areas whence 

 the supplies of ice had been derived. These would include boul- 



