The upper
plain of Santa Cruz slopes up to a height of 3000 feet at the foot
of the Cordillera. I have said that within the period of existing
sea-shells, Patagonia has been upraised 300 to 400 feet: I may add,
that within the period when icebergs transported boulders over the
upper plain of Santa Cruz, the elevation has been at least 1500
feet. Nor has Patagonia been affected only by upward movements: the
extinct tertiary shells from Port St. Julian and Santa Cruz cannot
have lived, according to Professor E. Forbes, in a greater depth of
water than from 40 to 250 feet; but they are now covered with
sea-deposited strata from 800 to 1000 feet in thickness: hence the
bed of the sea, on which these shells once lived, must have sunk
downwards several hundred feet, to allow of the accumulation of the
superincumbent strata. What a history of geological changes does
the simply-constructed coast of Patagonia reveal!
(PLATE 39. RAISED BEACHES, PATAGONIA.)
At Port St. Julian, in some red mud capping the gravel on the
90-feet plain, I found half the skeleton of the Macrauchenia
Patachonica, a remarkable quadruped, full as large as a camel.
(8/12. I have lately heard that Captain Sulivan, R.
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