137 



One does not see how the fact could well be otherwise, except as 

 in the case of some of our oldest masses of ice. In Greenland, I 

 conceive, and to a certain extent also in the Alps, we have to 

 remember that glaciation has probably gone on almost continuously 

 from late Pliocene times down to the present day; and any loosened 

 and disintegrated rock material that may at one time have formed 

 the surface rasped by the ice, has been long since removed, so 

 that the ice has none but sound and unweathered rock to work at. 

 In such cases, if no land rises above the level of the ice to furnish 

 by its atmospheric waste the material for surface moraines, the ice 

 may well be clean and free from detritus. It is significant, if Mr. 

 CroU's views are correct, that mention of stony and muddy ice 

 should be made more often in connection with the icebergs of the 

 Antarctic regions than with those of the Arctic. In the North the 

 Glacial Period is now waning, and the rock-surfaces have been 

 ploughed and rasped down to the very heart of the rock ; while in 

 the Antarctic region the Glacial Period has not long set in, and 

 the preglacially-weathered rock of that part has only just been 

 attacked. Be the explanation what it may, there can be no doubt 

 that vast quantities of stony material do occur in, as well as on, 

 modern icebergs. And as icebergs are nothing but large floating 

 masses broken off from larger masses of ice on land, it follows 

 that these masses of land ice are themselves charged more or less 

 with stones and mud. 



Distribution of Detritus through the Ice Sheet. — If the reader 

 have followed the observation made in the first part of this paper 

 relative to the means whereby stones and mud worked their way 

 into ice, as well as to their distribution hither and thither in the 

 ice under the action of currents, and also to their circulation from 

 one platform to another under the action of the complex forces at 

 work throughout the whole period of glacial action, he should 

 have no difficulty in forming some kind of idea of what must have 

 been the state of the Ice of the Glacial Period in this respect at 

 the time when it had come to a standstill and liquefaction had 

 commenced. Take the case of the ice over where, thousands of 



