The Willamette Sound [pp. 468-473]

THE WVILLAMETTE SOUND.
which we started from the capes of the
Columbia.
Nor is there any room for mistake
here; for while this fossil sediment extends through a vertical range of more
than I50 feet, the least total altitude that
will meet the conditions of the problem
must take in the highest portion of this
fossil bed. Stating this at 250 feet
above the present level of the river, is
placing it at its lowest, and even then
with the understanding that we are dealing with sediment, and not with surface lines. Nor yet will it do to set
these facts to the credit of that. system of river terraces known to exist
throughout the northern portion of our
continent. These, as recently described
from Frazer River, by Chief Justice Begbie, of British Columbia, and as described, years ago, by Professor Dana, from
Oregon and California, and still later, in
a recent number of The Am rican 7ournal of Science, in which they are designated as "part of a system of terraces
that covers a large part of North America north of the Ohio, and existing on
all streams, as far as examined, nearly
to their heads in the mountains."
Now, our facts and these-exclusively
inland facts -refuse to be classed together. The system of old shore-lines
we are tracing belongs primarily to the
sea-shore. These other terraces run inland, high among the mountains. The
facts upon which our theory was based
were gathered at Shoalwater Bay, were
controlled entirely by the level of the
Pacific Ocean, and scarcely affected by
flood-levels in the river, and still less by
any extended lake system of the interior.
And now, with our amended theory in
mind, as a measuring-rod, let us retrace
our steps to the lower country-the Willamette Sound of the olden time. Let
the fall of the Columbia River, from this
lake-shore east of the Cascade Mountains to the mouth of the Willamette
River, be stated at eighty feet. Our
fossil remains on this lake-shore are 250
feet above the present level of its waters,
making a total of 330 feet as the depth
of those waters above the present surface
at the mouth of the Willamette River.
How naturally one looks to the currents of such a vast body of water as the
agency competent to the heaping up of
that long sandy ridge, one hundred feet
high, through which the river has cut its
way at Swan Island, north of Portland.
But let us follow it still farther inland.
Over where Portland now stands, these
waters were 325 feet deep; over Salem,
I65 feet; over Albany, II5 feet; over
Tualatin Plains, I45 feet; over Lafayette, I70 feet. A narrow strait, over the
present valley of the Tualatin River, ten
or twelve miles in length, opened westward upon a broad, beautiful bay, extending over the present sites of Hillsboro and Forest Grove, to Gale's Peak,
among the foot-hills of the Coast Range.
The subsoil of the fine farms of that rich
agricultural region, is itself the muddy
sediment of that bay. Farther south,
over the central portion of the present
valley, and lying obliquely across the
widest part of that Willamette Sound,
there arose above those waters an elevated island. It extended from a point
south of Lafayette to one near Salem,
and must have formed a fine central object in the scene. Three or four volcanic islands extended, in an irregular
semicircle, where Linn County now is;
and the islands of those waters are the
Buttes of to - day - Knox's, Peterson's,
and Ward's. One standing on the summit of either of these Buttes, with the
suggestions of these pages before him,
could so easily and vividly imagine those
waters recalled, as to almost persuade
himself he heard the murmuring of their
ripples at his feet-so sea-like, the extended plain around him-so shore-like,
that line of hills, from Mary's Peak, on
the west, to Spencer's Butte, on the
472
[Nov.