261 Geology and Botany of Northern Pacific Nailroad. 

 THE LOWER COLUMBIA. 



The country bordering the Lower Columbia is too well-known 

 to require detailed description. I am compelled, however, to 

 refer to one or two points in its physical structure, which are of 

 special interest when brought into connection with facts of simi- 

 lar import observed in the region about Pnget's Sound. I have 

 said that the Lower Columbia is an arm of the sea. It is in fact 

 a deep river valley which has been flooded by an influx of the 

 sea caused by subsidence. This brings the tide-water to the foot 

 of the falls of the Willamette at Oregon City, and to the Cas- 

 cades. It requires no argument to prove that such a channel 

 could not have been cut unless by a rapid stream flowing into 

 the ocean when it stood at a lower level. Whether the change 

 in the relative level of land and sea here remarked was part of a 

 general movement that produced the influx of the sea into the 

 fiords which fringe the northern coast ; and whether this is nbt a 

 part of a still grander movement that flooded the old excavated 

 valleys of the James River, the Potomac, the Schuylkill, the 

 Hudson, the St. Lawrence and the Saguenay, and at the same time 

 filled the fiords of the northeastern coast, are questions which 

 cannot now be fully answered, but are worth considering. 



It will be noticed that the general plan of the topography of 

 this part of the coast is altogether similar to that of California ; 

 namely, the great wall of the Cascades, bordered on the west by 

 the Willamette and Cowlitz valleys and the Coast Mountains, 

 are re-produced further south by the Sierra Nevada, the great 

 California valley, and the Coast Ranges ; and their topographical 

 features are not only physically similar, but are geologically iden- 

 tical, the Cascades being the northern continuation of the Si- 

 erra Nevada, the more modern Coast Mountains following con- 

 tinuously the coast line ; the great trough between them being 

 essentially one, but filled, in its centre, by a mass of mountains. 



The forests of the country bordering the lower Columbia are 

 a physical feature that will strike every traveler with surprise 

 and admiration. They are also of primary importance economi- 

 cally, since they form the basis of the most important industry 

 of the northwest coast. They are mostly composed of evergreen 

 trees which attain an altitude of 200 to 300 feet, and are crowded 



