During the few succeeding days we
continued to get on slowly, for we found the river-course very
tortuous, and strewed with immense fragments of various ancient
slaty rocks, and of granite. The plain bordering the valley had
here attained an elevation of about 1100 feet above the river, and
its character was much altered. The well-rounded pebbles of
porphyry were mingled with many immense angular fragments of basalt
and of primary rocks. The first of these erratic boulders which I
noticed was sixty-seven miles distant from the nearest mountain;
another which I measured was five yards square, and projected five
feet above the gravel. Its edges were so angular, and its size so
great, that I at first mistook it for a rock in situ, and took out
my compass to observe the direction of its cleavage. The plain here
was not quite so level as that nearer the coast, but yet it
betrayed no signs of any great violence. Under these circumstances
it is, I believe, quite impossible to explain the transportal of
these gigantic masses of rock so many miles from their
parent-source, on any theory except by that of floating icebergs.
During the two last days we met with signs of horses, and with
several small articles which had belonged to the Indians--such as
parts of a mantle and a bunch of ostrich feathers--but they
appeared to have been lying long on the ground.
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