Even if you have never learnt much of what is called geology, by keeping
your eyes open and your mind awake you may see a great deal in the stones
which have perhaps seemed to you most uninteresting. A block of granite
from one of the Dartmoor hills, and a piece of slate from a Welsh
quarry--how different these two kinds of stone are! We see this at once;
but they become much more interesting when we know that each has its own
history. The granite is one of the fire-made rocks, so called because there
are marks upon it, like letters written long ago, quite plain to those who
have the skill to read them; which show that though it is now so hard, it
was once soft, as soft as iron becomes when melted by very great heat.
The mountains of Devon and Cornwall, the Grampians of Scotland, even Mont
Blanc, the "Monarch of Mountains," are made of the grey or red granite
which takes such a beautiful polish when cut that it is much prized for
buildings.
The piece of slate has quite a different history. It is one of the
water-made rocks, in which so many fossils have been found; while in
the fire-rocks there are no remains of anything which ever lived. The
water-rocks are so called because water has had so much to do with the
making of them; for they have been very slowly formed by the gravel and
grains of sand which have been washed down by streams and torrents, and
left behind in their course. In these slate and sandstone rocks the
wonderful fossil animals, which are to be seen in the Museum, have been
found.
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