THE GLACIER'S TOOLS. 69 



glacier's tools, which it holds fast with more than a giant's 

 grip and strength, and with which it either smooths and 

 rounds the rocks over which it passes, or else scores them 

 'with deep grooves and ruts. 



In the summer, when the glacier shrinks away from the 

 sides of its bed, it is possible to creep in below the ice and 

 to see both the long scratches made on the rocks and how 

 finely these have been smoothed and polished by the sand, 

 mud, and smaller stones, which result from the perpetual 

 grinding of this mighty millstone. 



Some of the great Arctic glaciers, which are often two or 

 three thousand feet thick, must exert enormous pressure on 

 the blocks and sharp-edged fragments of stone imprisoned 

 beneath them, and their beds are accordingly in some places 

 as smooth as a polished agate, and in others are covered with 

 grooves, which in time become deep furrows. 



Streams of water flow beneath every glacier, and gushing 

 forth at its foot, densely charged with the finest mud, form 

 the source of many a river ; but the pebbles conveyed by a 

 glacier stream differ from those of other streams, in that they 

 are usually angular ; and the glacier is not nearly such a 

 neat workman as the river, for instead of sorting its load, 

 dropping the large pebbles here, the smaller there, the gravel 

 in one place and the fine sand in another, the glacier just 

 drops its immense piles of sand, grit, stones, huge slabs and 

 rocks all together, and heaps them up anyhow into one great 

 mound. 



In other respects the action of the glacier is so like that 

 of the river that, but for the peculiar tokens of its presence 

 in the shape of rounded, scratched, and polished rocks, there 



