It is only found in rocks which have been
subjected to immense pressure, and probably to heat. The granites
and mica-slates of Anglesey are full of it; and from Anglesey--as
likely as from anywhere else--these thin scales of mica came. And
that is about all that I can say on the matter. But it is certain
that most of these sands were deposited in a very shallow water, and
very near to land. Sand and pebbles, as I said in my first paper,
could not be carried far out to sea; and some of the beds of the
Bunter are full of rounded pebbles. Nay, it is certain that their
surface was often out of water. Of that you may see very pretty
proofs. You find these sands ripple-marked, as you do shore-sands
now. You find cracks where the marl mud has dried in the sun: and,
more, you find the little pits made by rain. Of that I have no
doubt. I have seen specimens, in which you could not only see at a
glance that the marks had been made by the large drops of a shower,
but see also from what direction the shower had come. These delicate
markings must have been covered up immediately with a fresh layer of
mud or sand. How long since? How long since that flag had seen the
light of the sun, when it saw it once again, restored to the upper
air by the pick of the quarryman? Who can answer that? Not I.
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