GEOLOGY-TERRACES—COAST MOUNTAINS-PORT ORFORD. 
59 
proved to be nearly worthless as fuel. It occurs in argillaceous sandstone, apparently forming 
a portion of this series. 
Terraces .—At Vancouver the hanks of the Columbia are distinctly terraced. The alluvial 
bottom lands had an elevation of twenty feet above the surface of the water during the month 
which I spent there ; but at certain seasons, as evinced by the collected drift wood, are liable to 
overflow. Above this level the terrace upon which the fort stands rises to a height which I 
estimated at forty feet. This terrace is found bordering not only the Columbia, but also the 
Willamette, and is the one upon which the town of Portland is built. Prom any elevated point 
where a view can be obtained over the dense forest which covers the country bordering the 
Willamette river near its mouth this terrace is seen to be distinctly marked by the summits of 
the trees, and may thus be traced for miles. The soil of the alluvial lands bordering the 
streams is fine, dark, and very fertile ; that of the upper terrace is frequently gravelly and less 
productive. 
COAST MOUNTAINS. 
The Columbia, from the mouth of the Willamette to the ocean, forms rather an arm of the sea 
than a river channel. It is broad, in many places deep, and on either side bordered by marshes 
and swamps, which have the appearance of having been depressed below the level which they 
once occupied. Its bed is nowhere formed of rock, but seems like a trough, broadly and deeply 
excavated, and subsequently silted up by the sediment, which an arrested current no longer 
held in suspension. 
The mountains which rise on either side form a broad belt, marked by no summit of great 
elevation, and everywhere covered with a dense evergreen forest. I had little opportunity of 
examining their geological structure, but noticed at various points masses of trap, and along 
the river, near its mouth, at a lower elevation, beds of tertiary sandstones and shales. Near 
Astoria these strata are fully exposed, but, in the brief time that I remained there, I was able 
to do little more than note the remarkable similarity, in lithological character, which they 
exhibit to those of San Francisco and San Pablo bay. Many species of fossils were, however, 
collected from the same series in this vicinity by Professor Dana, and have been described by 
Mr. Conrad in the geology of the exploring expedition. They have been regarded by him 
as of Miocene age, though containing no recent species, nor any previously described, from 
tertiary rocks in other localities. These fossils are chiefly molluscous, with bones of cetaceans 
and fishes. They are usually found forming the nuclei of calcareous concretions. 
PORT ORFORD. 
From the mouth of the Columbia to this point the coast presents a bold, irregular outline, 
with scarcely any level land along the shore. It is everywhere covered with a dense forest, and 
that portion north of the Umpqua river has been but rarely traversed by explorers. Of its 
geological structure almost nothing is known, except of the small portion visited by Professor 
Dana, in his excursion to the Saddle mountain, near Astoria. This mountain, as might be in¬ 
ferred from its outline, is volcanic, and has been in action at a comparatively late period. 
The geology of the vicinity of Port Orford is similar, in all its general features, to that of 
Astoria. The high lands in the vicinity, as well as the bold and rocky points on the shore, are 
composed of trap rock. Beds of sandstone line the coast north of Port Orford, closely 
resembling the sandstones and shales of Astoria, and probably belonging to the same series. 
