40 
stone, forming the cliffs on the coast of Fife, were almost entirely 
eaten away by the air in this manner, and this within the lapse of 
a few hundred years. 
The mechanical action of running water need not be demonstra- 
ted, and its extent would be appreciated by all who had visited moun- 
tainous districts since they became acquainted with the principles of 
geology. And no one who had carefully watched the action of a 
stream would fail to conclude that the valleys had been carved out, the 
hills sculptured, by the very agents now at work. 
The chemical action of the air and rain-water was continually 
disintregrating and dissolving the rocks, the freezing of the water 
among their crevices was yearly shattering them, and the heavy rain- 
fall and flowing water was for ever bearing away the loosened material 
to lower and lower levels. Nor was the action of ice in the form of 
glaciers to be forgotten ; it had been a powerful agent in this country 
and was now in Switzerland. A glacier was a river of ice (representing 
the snow drainage of the mountains), but flowing very much more 
slowly than an ordinary river. The frost constantly detached | 
blocks of stone from the snowless peaks ; they fell upon the ice and 
were carried onwards with the glacier, forming long lines upon its 
surface, and when it ended they were shot off and formed mounds of 
stony rubbish called terminal moraines. But the ice had another 
effect. Moving slowing over its rocky bed, it smoothed, ground, 
polished, and scratched it, rounding the rocks in a very marked 
manner, and often leaving large blocks of stone perched upon them. 
The whole of the English Lake district had been thus ice-worn ; in 
every valley the rounded and scratched rocks could be traced as well 
as the old moraines left by the retiring glaciers. Insignificant as many 
of these agencies appeared, they only required sufficient time to pro- 
duce effects equal to those produced by powerful agents acting for a 
short time. 
How far was the effect of these agencies varied by the peculiarities 
of the rocks in structure and composition? Taking Derwentwater, 
nothing could be more distinct than the mountain forms on either side 
the lake—on the one all rough and craggy, on the other smooth and 
sloping. The cause was not far to seek. 
On the east side the mountains were formed of hard volcanic rocks, 
continually being shattered by the weather. On the west side the 
mountains were formed of Skiddaw slate, which instead of breaking 
away in large fragments, shivered into small scales; the waste of these 
