RIVER TERRACES. 665 
Sacramento Bute. There is no regular deposit of alluvium on its 
sides, but pebbles of quartz and jasper, like those of the pebbly upper 
plain, cover the outer declivities to a height of one hundred and fifty 
feet above the level of the prairie. 
The Sacramento Plains were estimated to be six miles wide where 
we first reached them. At the Bute, the width is about thirty miles, 
and at Captain Suter’s, as he informed me, near fifty miles. The plains 
continue to Caquines Straits, at the head of the Bay of San Francisco, 
twenty miles from the sea, where the hills of the Coast Range confine 
the river, and intercept the alluvial flats. 
Columbia River.—The only place on the Columbia where I ob- 
served the terrace of this region was at Vancouver. Back of the fort, 
about half a mile from the river, there is a terrace of forty-five or 
fifty feet. To the westward the terrace gradually melts away into a 
longer and more gentle slope. Eastward, it may be traced for three 
miles, nearly to the grist-mill, where it meets the river bank ; but it 
is mostly covered with forests. At the grist-mill, in the bed of the 
stream, there is a compacted deposit of pebbles, about thirty-five feet 
above the river, which resists the action of the water, and stands out 
in projecting ledges, though still so yielding that it may be dug out 
with a pickaxe. This bed is probably a part of the old or upper 
alluvium. 
The river at Fort Vancouver has banks twenty feet high; but here, 
as elsewhere about the rivers, the bottom-land situated at this height, 
is mostly flooded during the freshets. 
In the Upper Columbia, about Wallawalla, the same terrace was 
observed by Mr. Drayton, and the following particulars have been fur- 
nished by him. The great Wallawalla plain lies about ten feet above 
flood water in the Columbia. This plain is nearly level, but rises a 
little from the shores. Ten miles east, there is a series of gravel hills, 
showing a perpendicular front towards the plain, thirty or thirty-five 
yards high, consisting of alternating beds of earth, gravel, pebbles and 
large rounded stones. ‘The pebbly layers were most abundant one- 
third of the way to the top. ‘The base of these bluffs is forty or forty- 
five yards above the river. ‘They stretch around to the southward, at 
the base of the higher basaltic hills, and may be traced for several 
miles. 
From our philologist, H. E. Hale, we learn that above the Dalles, for 
a long distance, the valley of the Columbia widens to two miles, and 
is enclosed between two unbroken lines of basaltic hills, five hundred 
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