54 TOWN GEOLOGY. [n, 



We find underneath the glaciers, first a moraine- 

 prof onde, consisting of the boulders and gravel,, and 

 earth, which the glacier has ground off the hillsides, 

 and is carrying down with it. 



These stones, of course, grind, scratch, and polish 

 each other ; and in like wise grind, scratch, and polish 

 the rock over which they pass, under the enormous 

 weight of the superincumbent ice. 



We find also, issuing from under each glacier a 

 stream, carrying the finest mud, the result of the 

 grinding of the boulders against each other and the 

 glacier. 



We find, moreover, on the surface of the glaciers, 

 moraines superieures long lines of stones and dirt 

 which had fallen from neighbouring cliffs, and are 

 now travelling downward with the glaciers. 



Their fate, if the glacier ends on land, is what was 

 to be expected. The stones from above the glacier 

 fall over the ice-cliff at its end, to mingle with those 

 thrown out from underneath the glacier, and form 

 huge banks of boulders, called terminal moraines, 

 while the mud runs off, as all who have seen glaciers 

 know, in a turbid torrent. 



Their fate, again, is what was to be expected if the 

 glacier ends, as it commonly does in Arctic regions, in 

 the sea. The ice grows out to sea-ward for more than 

 a mile sometimes, about one-eighth of it being above 

 water, and seven-eighths below, so that an ice-cliff one 

 hundred feet high may project into water eight 

 hundred feet deep. At last, when it gets out of its 

 depth, the buoyancy of the water breaks it off in ice- 

 bergs, which float away, at the mercy of tides and 

 currents, often grounding again in shallower water, 



