The lower country consists of clay-slate and sandstone, containing
fossils, very closely related to, but not identical with, those found
in the Silurian formations of Europe; the hills are formed of white
granular quartz rock. The strata of the latter are frequently arched
with perfect symmetry, and the appearance of some of the masses is in
consequence most singular. Pernety [8] has devoted several pages to
the description of a Hill of Ruins, the successive strata of which he
has justly compared to the seats of an amphitheatre. The quartz rock
must have been quite pasty when it underwent such remarkable flexures
without being shattered into fragments. As the quartz insensibly
passes into the sandstone, it seems probable that the former owes its
origin to the sandstone having been heated to such a degree that it
became viscid, and upon cooling crystallized. While in the soft state
it must have been pushed up through the overlying beds.
In many parts of the island the bottoms of the valleys are covered in
an extraordinary manner by myriads of great loose angular fragments of
the quartz rock, forming "streams of stones." These have been mentioned
with surprise by every voyager since the time of Pernety. The blocks
are not water-worn, their angles being only a little blunted; they vary
in size from one or two feet in diameter to ten, or even more than
twenty times as much. They are not thrown together into irregular
piles, but are spread out into level sheets or great streams. It is
not possible to ascertain their thickness, but the water of small
streamlets can be heard trickling through the stones many feet below
the surface. The actual depth is probably great, because the crevices
between the lower fragments must long ago have been filled up with
sand. The width of these sheets of stones varied from a few hundred
feet to a mile; but the peaty soil daily encroaches on the borders, and
even forms islets wherever a few fragments happen to lie close
together. In a valley south of Berkeley Sound, which some of our party
called the "great valley of fragments," it was necessary to cross an
uninterrupted band half a mile wide, by jumping from one pointed stone
to another. So large were the fragments, that being overtaken by a
shower of rain, I readily found shelter beneath one of them.
Their little inclination is the most remarkable circumstance in these
"streams of stones." On the hill-sides I have seen them sloping at an
angle of ten degrees with the horizon; but in some of the level,
broad-bottomed valleys, the inclination is only just sufficient to be
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