HOW SCENERY IS MADE 
27 
Besides in Wales, where the rocks are particularly hard, deep 
river valleys are seen abundantly elsewhere. Thus there is the 
beautiful valley of the Wye, south of Ross, those of the streams 
at Stroud and elsewhere, in Gloucestershire, and of others in 
Derbyshire, as at Matlock, &c. Though the valleys are now 
deep and wide, with comparatively small streams at their 
bottoms, which look too insignificant to have washed away so 
much material, or to have scooped out their sloping troughs, 
yet if we give them time we may credit them with having done 
nearly the whole of the work. 
As a proof that the river has really done the work, if the 
strata or beds of rocks be examined on opposite sides of the 
valleys, they will often be found to correspond ; just as when 
you take a bite out of a sandwich, the layers of bread and meat 
were once continuous across the gap. 
While the river goes on deepening its own channel, we must 
now give the atmosphere its due ; for rain falling on the sloping 
sides washes away the soil, which gradually gets carried down 
to the river and is soon conveyed away, so that the breadth of 
the trough of' a valley, through any district where the rock can 
be “ disintegrated ” or decomposed, becomes wider and wider 
as well as deeper. In Wales, however, the rocks are mostly 
too hard for this, so that the rivers have precipitous sides, as 
at Dolgelly, &c. 
If the sloping sides be covered with grass, this is some pro- 
tection against their being washed away ; but the soil below 
is nevertheless constantly going, as may be seen by the innumer- 
able little “ earth-slips,” as they may be called, which, when 
looked at from a distance, appear to be narrow “ sheep-walks ” 
or minute little terraces, often joined by oblique ones. Follow 
them down to the water’s edge and they may often there be 
een to be breaking away and tumbling into the river. 
Rivers thus provide us with various kinds of scenery, accord- 
ing to the nature of the country and of the rocks they pass over. 
There is another feature, but it is a local one. If the under- 
lying rock be a limestone, a great deal of the rain passes into 
the cracks which always occur in such rocks, and by dissolving 
them, the cracks widen, so that larger quantities of water pass 
underground forming a channel for itself, and escaping at some 
lower level. The result, after incalculable ages, is that even a 
large river may flow for miles underground, passing through 
enormous caves, these having been formed by blocks falling 
down, which are then broken up, dissolved, and carried away. 
As the water continually drips from the roof and evaporates, 
it leaves a deposit of “ carbonate of lime,” forming large icicle- 
like structures called “ stalactites,” and if it accumulate on the 
floor it is called “ stalagmite.’’ These may be seen plentifully 
in Derbyshire. Occasionally the roof falls in, leaving a great 
hole perhaps in the middle of a field. In some such hole a river 
may suddenly plunge and disappear, to reappear several miles 
