430 Glaciers. 



to distinguish from that marine drift which, at equal 

 levels, covers so much of the country further south. 



There is often great difficulty in distinguishing be- 

 tween these latter moraines and the great masses of 

 moraine-matter that were formed during that earlier 

 period when the northern ice-sheet covered the greater 

 part of Britain, and which undoubtedly were not ter- 

 minal, but actually lay under the ice moraines pro- 

 fondes, as they have been termed by French and Swiss 

 geologists. Neither is it always easy to distinguish 

 between this ' Till ' and the marine glacial drift when 

 shells are absent, for the plains of the latter melt into 

 gentle slopes of glacial debris that pass far up the valleys, 

 and on the hill-sides over many high watersheds. 



One reason for this difficulty is that, in certain 

 stages of the history of the period, the larger sheet or 

 sheets of glacier-ice covered the hills and filled the 

 valleys so thickly and completely that, pushing out to 

 sea, they even excluded it from parts of valleys that 

 were at a lower level than the sea itself; and moraine- 

 matter thus got sorted and mingled with other marine 

 deposits. This partly accounts for the gradual merging 

 of those marine gravelly mounds, called Kames or 

 Eskers, into Boulder-clay and true moraine heaps full of 

 ice-scratched stones. The Eskers themselves are often 

 largely charged with water-worn stones originally well 

 ice-scratched. These glacial scratchings have since 

 been almost entirely worn away by friction, the stones 

 having been rubbed against each other by moving water. 

 The mere ghosts of the original sharp scratchings now 

 remain. 



The foregoing sketch of the Glacial epoch is of 

 much importance in a geological point of view, more 

 especially because of the pictures we get of phases of a 



