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the low ground surrounding it is formed of soft Skiddaw Slate. 
Or again, if in walking from Rosthwaite towards Keswick, we 
enquire why the valley along which we walk widens out so suddenly 
at the village of Grange, and we are told that we are then just 
leaving the volcanic lavas and ashes, and coming upon the softer 
Skiddaw Slates; the reason for the sudden change in the width ot 
the valley at once flashes upon us, and we are satisfied. 
Or generally, suppose we ask ourselves why some valleys are 
deep and narrow, whilst others are broad and shallow, what 
answer can we give? The reply involves a knowledge of the 
process of valley formation. Suppose we have a stream that has 
just commenced to cut its way through a newly formed tract of 
country, as for instance a piece of flattish country that has just 
been raised out of the sea;—as soon as ever that stream has 
formed for itself a channel, the sides of that channel will be 
attacked by the various chemical and meteoric denuding agents. 
Frost, if it be in winter, will loosen and crumble large quantities 
of rock on each side of it. Water charged with carbonic acid will 
dissolve and carry much away, especially if the rock be either 
chalk or limestone; and the pieces loosened and crumbled by 
frost will be washed by rain into the stream, and thereby carried 
away to be deposited elsewhere. The effect of these united actions 
will be that the channel will soon become wider at the top than at 
the bottom; for the top having been longer exposed to the 
denuding agents, must necessarily have suffered more from them. - 
In course of time, as the stream deepens its bed, either by erosion 
or by dissolving the material of which it is composed, fresh ex- 
posures of rock will take place along the bottom of each bank, 
which will at once be attacked and wasted by the impatient 
destructives. So also will every additional exposure that is made 
by deepening the stream bed, no matter how long that may be 
continued. The result of these actions ultimately will be a valley. 
As the stream worked itself deeper into the rock, the sides or 
banks would be worn gradually further and further back by frost 
and rain and chemical decomposition. The upper part of each 
bank having been longer acted upon by these influences than the 
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