1855.] ISBISTER — NORTH AMERICA, ETC. 517 



Colville there is a range of heights, which extends along the north 

 hranch of the Columbia River, and may be considered a part of the 

 same general chain. 



The short western slope of the continent from the Rocky Moun- 

 tains to the Pacific differs from the eastern in its river-valleys being 

 all more or less transverse, — the rivers flowing through passes or 

 gorges of the intersecting ranges. The peculiar wing-like projection 

 in the north, towards Asia, is evidently due to the volcanic chain of 

 Aliaska, which runs at right angles to the Rocky Mountains. The 

 great transverse valley of the Yukon (the Kwichpack of the Russian 

 geographers) lies to the north of it. The Yukon is a river of great 

 magnitude, probably the largest river in America flowing into the 

 Pacific, not excepting the Columbia. For a considerable part of its 

 course it flows to the north, but afterwards nearly due west, through 

 a country which, as far as can be judged from the descriptive notices 

 of it hitherto collected, closely resembles the valley of the Mackenzie, 

 with some of the afiluents of which it is in fact connected ; so that 

 here, as in other parts of the Rocky Mountain Chain, the rivers fall- 

 ing into opposite seas interlock at their origin. One or more low 

 chains of mountains, formed by the lateral spurs of the Rocky 

 Mountains, are prolonged along the Arctic Coast, north of the 

 Yukon, giving origin to several small rivers between the mouth of 

 the Mackenzie and Point Barrow. 



Oregon Territory. — Our acquaintance with the geology of this 

 district is very limited, and does not extend beyond the portion of 

 country between the Coast Range and the sea, explored, by the Expe- 

 dition of Commodore Wilkes. From Mr. Dana's researches it appears 

 to be occupied chiefly by the tertiary formation, which is found at 

 various places from Puget's Sound to San Francisco along the coast- 

 section of Oregon. The rocks of this formation are soft sandstones, 

 more or less argillaceous and schistose, and clay-shales, either firm or 

 crumbling, together with tufa and conglomerate. The sandstones 

 and shales have been denuded on a vast scale. Although the rocks 

 are nearly or quite horizontal wherever examined, there are no plains 

 on the coast-section excepting those of alluvial origin. Mr. Dana 

 considers that the Coast Range, by which the Pacific coast was ele- 

 vated, was formed while igneous action was going on in the interior, 

 where the frequent changes of the river-basins and other indications 

 of a similar kind afford evidence of extensive and very recent vol- 

 canic disturbance. 



The fossils collected by Mr. Dana were examined by the eminent 

 conchologist Mr. T. Conrad, who assigned them to the geological 

 aera of the Miocene. They are comprised in the following list. 



Mammal. 

 1. Vertebra of a Cetacean. 



Fishes. 



1. Vertebra of a species of Shark. 



2. of a species allied to Tregla. 



3. , cast of ; species not distinguishable. 



