GEOLOGY. 327 



- 



canon nearly an hundred miles in length. The Klamath basin was once to 

 a much greater extent covered by water than now ; and before it was so 

 perfectly drained as now, its waters deposited a variety of strata, some of 

 which were as white and fine as chalk, though having a very different com- 

 position. 



He said further, that the basin or plateau of the Des Chutes was not sepa- 

 rated by any barrier from that of the Klamath lakes, and exhibited all its 

 peculiar features still more strongly marked. The Des Chutes basin was a 

 plateau lying between the Cascades and the Blue Mountains,- and, with the 

 Klamath basin, belonged, from its topography, geology, fauna, flora, and 

 climate, to the great central basin. Like the Klamath basin it was once 

 covered with water was a lake drained by the Columbia, as now, but not so 

 perfectly drained. The Columbia had been gradually deepening its bed. The 

 Des Chutes lake, as it then was, had deposited sediments to the depth of 

 2.000 feet or more, for the streams which now traverse it have cut canons in 

 this plateau to that depth. These sediments were covered by a floor of trap 

 which had been poured evenly over the whole surface which had not been 

 subsequently disturbed, and when broken open, exhibited a columnar struc- 

 ture the columns being quite perpendicular and sometimes one hundred feet 

 in height. Below the trap was a series of strata exhibiting ah 1 possible varie- 

 ties of volcanic tufa, some very fine and chalky, others coarser ; and the 

 different layers, which were from two to ten feet in thickness, and perfectly 

 parallel, were colored with all the hues of the rainbow red, green, yellow, 

 blue, orange, pink, white, &c., and as highly colored as a geological chart for 

 a lecture room. It had often happened to him, travelling over this plateau, to 

 come suddenly and without any warning to the brink of one of these canons 

 two thousand feet deep, at the bottom of which a stream was flowing. 



The Cascade Mountains, he said, were not a simple chain, but a broad belt 

 of mountain peaks, sometimes fifty miles or more in width, many of the sum- 

 mits being covered with perpetual snow, the passes being generally about 

 7,000 feet in height. He had found extensive proofs of the existence, at a 

 former period, of glaciers capping the Cascade range, and extending far below 

 the present limit of perpetual snow. The Cascade range was eminently 

 volcanic, abounding in craters, lava fields, and congealed lava streams, all as 

 fresh and ragged as though just poured out from some volcano ; indeed, 

 Mount Hood and Mount St. Helens maystiU be considered as active vol- 

 canoes, giving off gases and steam continually, and within a few years have 

 emitted showers of ashes. 



Professor jST.'s theory of the excavation and filling of the valleys of California 

 and Oregon was, that at one time, probably at a period corresponding with' 

 that of the drift in the Eastern States, ah 1 that portion of the continent wag 

 raised to such an altitude as to produce a degree of cold which covered the 

 mountains and filled the valleys with ice. By this ice the surfaces of rock 

 were worn down, and the marks of glacial action which now abound pro- 

 duced. The valleys were excavated hi part by this process. As the continent 

 was depressed the valleys were occupied by water, in which the ashes from 

 ranges of active volcanoes were discharged, and arranged in strata of sediment. 



