124 THE FAIRY-LAND OF SCIENCE. 
come flowing smoothly in and have no power to eat 
away the shore. 
And now, what has Ice got to do with the sculp- 
turing of the land? First, we must remember how 
much the frost does in breaking up the ground. The 
farmers know this, and always plough after a frost, be- 
cause the moisture, freezing in the ground, has broken 
up the clods, and done half their work for them. 
But this is not the chief work of ice. You will 
remember how we learned in our last lecture that 
snow, when it falls on the mountains, gradually slides 
down into the valleys, and is pressed together by the 
gathering snow behind until it becomes moulded into 
a solid river of ice (see Fig. 31, Frontispiece). In 
Greenland and in Norway there are enormous ice- 
rivers or glaciers, and even in Switzerland some of 
them are very large. The Aletsch glacier, in the Alps, 
is fifteen miles long, and some are even longer than 
this. They move very slowly on an average about 
20 to 27 inches in the centre, and 13 to 19 inches at 
the sides every twenty- four hours, in summer and au- 
tumn. How they move, we cannot stop to discuss 
now; but if you will take a slab of thin ice and rest 
it upon its two ends only, you can prove to yourself 
that ice does bend, for in a few hours you will find 
that its own weight has drawn it down in the centre 
so as to form a curve. This will help you to picture 
to yourself how glaciers can adapt themselves to the 
windings of the valley, creeping slowly onward until 
they come down to a point where the air is warm 
enough to melt them, and then the ice flows away in 
