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 banks 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. From 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. 



