tiro/,,,/ ii <t,t<l / / .\V///*r// Pacific Railroad, 



U timOB. Bet ween the rugged rock-ma-ses aiv lc\d >|, 



dotted over with bunch gras-. sage i 



The ;il .substructure , niarv 



beds of \;irius kinds, sedimentary vulcanic ash. washed ii..\\n 

 from tin- highlands, and diatomac, ou- earth. inter.M rat ilied with 

 sheet- of liasalt. It is evident that this belt was f.r a long 

 time, either wholly or in part. occupied hy lakes. l>uring 

 Ion- periods of ijuiet. all forms of life were ahundaiit : the land 

 supported a varied growth of arboiv>ccnt and herbaceous plants, 

 whieh furnished food to a great \arietvof animals, while the 

 water was inhabited by fishes and inollusks of many kinds. 

 At intervals, however. >howei> of ashes, ni"-tl\ -manat in<: from 

 the volcanic \ents of the Cascade Mountains. -overed th- cnun- 

 tay. destroyed, over larirr areas, all forms of animal and \ 

 table life, and washing into the lakes, formed strata man\ 

 in thiekness. At other times, floods of lava poured down into 

 this valley, spreading over the land and the lake-bottom-:, to be 

 covered airain in time with other sheets of stratified tufas, or b\ 

 fre>b- water fossiliferous beds. 



The Columbia. Snake River. .John Dav'> Kiver. thr I' 

 C'hutes. and many minor streams, cut deeply into this plain. 

 and expose in their banks sections of the beds described. In 

 the valley of the Des Chutes, dill's 1,000 feet in height 

 formed of them; and about the Dalles, the remains of hori/.on- 

 tal Tertiary beds are seen 2,0<n feet above the pre-rnt l-\-l <f 

 the Columbia. These >how that the lofty and continuous chain 

 of the Cascades formed a mighty dam. which kept back the 

 drainage of the interior so that it formed a MTU- of urc.it lake-. 

 bounded on the east by the Rocky Mountains, and on the west 

 b\ the Ca-cadcs. and separated into several basins by the Blue 

 Mountain.- and others of the desert ranges. 



The accumulated water found an outlet to the sea through tin- 

 lowest L r :ips in tl le Mountains. Of these. theiiio>t im- 



portant was that when the gorge of the Columbia is now situ- 

 ated : othen > \i>t further south and are now tra\er--d b\ the 

 the Klamath and 1'it I, 1 ). In the Oolun 



basin, the old lakes arc all draim-d. or tilled, and t heir bottoms 

 Are deep) j "-"red by the drain ins. The lake of the 



math ba<in i< now i-cpresetlted by th.- Klamath Lake-. -:ike, 



