How very much they have done toward making it you will be able to
judge for yourselves, if you will read the sixth chapter of Sir
Charles Lyell's new "Elements of Geology," or the first hundred pages
of that admirable book, De la Beche's "Geological Observer;" and
last, but not least, a very clever little book called "Rain and
Rivers," by Colonel George Greenwood.
But though rain, like rivers, is a carrier of soil, it is more. It
is a maker of soil, likewise; and by it mainly the soil of an upland
field is made, whether it be carried down to the sea or not.
If you will look into any quarry you will see that however compact
the rock may be a few feet below the surface, it becomes, in almost
every case, rotten and broken up as it nears the upper soil, till you
often cannot tell where the rock ends and the soil begins.
Now this change has been produced by rain. First, mechanically, by
rain in the shape of ice. The winter rain gets into the ground, and
does by the rock what it has done by the stones of many an old
building. It sinks into the porous stone, freezes there, expands in
freezing, and splits and peels the stone with a force which is slowly
but surely crumbling the whole of Northern Europe and America to
powder.
Do you doubt me? I say nothing but what you can judge of yourselves.
The next time you go up any mountain, look at the loose broken stones
with which the top is coated, just underneath the turf. What has
broken them up but frost? Look again, as stronger proof, at the
talus of broken stones--screes, as they call them in Scotland;
rattles, as we call them in Devon--which lie along the base of many
mountain cliffs. What has brought them down but frost? If you ask
the country folk they will tell you whether I am right or not. If
you go thither, not in the summer, but just after the winter's frost,
you will see for yourselves, by the fresh frost-crop of newly-broken
bits, that I am right. Possibly you may find me to be even more
right than is desirable, by having a few angular stones, from the
size of your head to that of your body, hurled at you by the frost-
giants up above. If you go to the Alps at certain seasons, and hear
the thunder of the falling rocks, and see their long lines--moraines,
as they are called--sliding slowly down upon the surface of the
glacier, then you will be ready to believe the geologist who tells
you that frost, and probably frost alone, has hewn out such a peak as
the Matterhorn from some vast table-land; and is hewing it down
still, winter after winter, till some day, where the snow Alps now
stand, there shall be rolling uplands of rich cultivable soil.
So much for the mechanical action of rain, in the shape of ice. Now
a few words on its chemical action.
Public-domain text, read in full here on John Shaqi.
Reviews
Reviews
No reviews yet
Be the first to share your thoughts on this work.
Join the Discussion
Join the discussion
Sign in to leave a comment or review.
Sign InorCreate an account