GEOLOGY AGE OF THE TUFAS OF DES CHUTES BASIN. 55 



these facts we must infer that the fauna and flora of that period were exceedingly meagre ; a 

 state of things which we might expect with the arctic temperature which should form glaciers 

 in the Cascades ; the drainage from which supplied these basins. 



The question of the age of the tufas of the basins east of the Cascade mountains is not without 

 its interest in this connexion, for, if they are of ancient date, it would be impossible to asso 

 ciate them with the modern and superficial phenomena of glaciers. We have every evidence 

 however, that, geologically speaking, they are very recent ; the unmineralized vegetable matter 

 which they contain proving this conclusively. They have evidently been formed of materials 

 thrown out and washed down from the volcanic peaks which crown the summit of the Cascade 

 mountains, and which have been in vigorous action within a few hundred years. Similar 

 deposits in the valleys west of the Sierra Nevada belong to a period subsequent to the tertiary, 

 as they contain the remains of the mammoth and mastodon, and are not older than the drift. 



On the plateaus of the Des Chutes and Klamath basins I was never able to detect the least 

 evidence of the action of drift currents. On the contrary, it was perfectly apparent that the 

 trap plateaus, the volcanic ridges, and the rough and ragged lava plains, had never been sub 

 merged, but presented surfaces in all respects similar to those first formed, except where covered 

 by a soil derived from the disintegration of the rock, through the agency of the atmosphere or 

 vegetation. I may say, in conclusion, that the glaciers of the Cascade mountains, stratified 

 deposits of great thickness, exhibiting nearly an entire absence of fossils, and not older than 

 the drift, large lakes once existing where now are only arid plains, and canons cut through 

 mountain walls, offer an interesting parallel with the stupendous phenomena, and evidences of 

 change elsewhere furnished by the drift, and afford, at least, presumptive evidence of synchronism. 



THE CANON OF THE COLUMBIA. 



GENERAL FEATURES. 



On any other supposition than that the gorge of the Columbia has been cut by the stream 

 now flowing through it, it becomes a matter of no little difficulty to account for its existence. 

 To the theory more commonly adopted, that it is a rift formed by volcanic forces, many objec 

 tions at once suggest themselves. 



Fissures caused by earthquakes or volcanic action have never been known to assume such a 

 form or direction. We should expect to find them, if at all in that region, radiating from 

 some one of the great foci of volcanic forces ; Mount Hood, Mount Jefferson, Mount Adams, or 

 Mount Baker ; while, on the contrary, we find this gorge traversing the entire, though com 

 pound chain, and afterward the Coast mountains, with a line of bearing which shows that the 

 forces which formed it did not centre in the peaks I have mentioned, nor any other of the range. 



We should also expect, if such was its origin, that other and similar fissures would be not 

 uncommon, or at least unknown in the mountain chain which it traverses ; but it is a singular 

 fact that, throughout the entire breadth of Washington and Oregon Territories, from the ) 

 British line to the boundaries of California, the Cascade mountains extend in a wall whose- 

 continuity is broken only by this single gorge. 



The lowest of its passes (Abbot s new pass) has an altitude of not less than 4,400 feet. In winter, 1 v 

 the chain cannot be crossed, and in summer the obstacles which it presents are such that loaded 

 mules are taken over with difficulty ; and yet through this barrier the Columbia flows nearly 

 at the sea level. 



