Explorations and Surveys for the Pacific Railroad. 75 



Dearborn river, which the road must cross. The summit of the 

 pass has an elevation of 6,044 feet ; and requires a tunnel 4J 

 miles long, at an elevation of 5,000 feet, with grades of approach 

 of 60 feet, and of departure of 40 feet, per mile. 



A tunnel 4J or even 2-§- miles in length, in rock or part rock, 

 at a depth below the summit of 1,000 feet, in a severely cold 

 climate, 800 or 1,000 miles distant from a thickly inhabited 

 district, is a work of vast difficulty ; and the necessity of the 

 construction of one of these two tunnels, in connexion with the 

 character of the approach, and the difficult nature of the work 

 required, continuing westward as far as the crossing of the Spo- 

 kane river, in all a distance of 365 miles, is one of the most se- 

 rious objections to the route. 



From either pass the route seeks the Blackfoot river, with the 

 view of reaching Clark's fork, which opens the only pass through 

 the Bitter Koot mountains, the practicability of which was de- 

 termined. * * - M 



* * Having reached Clark's fork, the route [the best of the 

 two proposed] continues along this river as far as Lake Pend 

 d' Oreille, between rugged, rocky mountains, which at several 

 points crowd upon the river. The valley of this river is heavily 

 timbered, principally with pine, and, with the lake, it is subject 

 to freshets fifteen feet in height. Leaving Lake Pend d' Oreille 

 at its lower extremity, the route crosses to the Spokane without 

 difficulty. At the Spokane river the continuous mountain re- 

 gion and the forest terminate, and "all great difficulties of loca- 

 tion upon the route cease." The earth-excavation and embank- 

 ment throughout this section (from the east base of the Eocky 

 mountains to the Spokane river, 365 miles) will be large in 

 amount, and expensive ; there will be frequent rock-excavation, 

 and the bulk of the rock-excavation in the entire route will be 

 in this section. It is evident that the difficulties of construction 

 will be great, and the cost excessive. * * * 



Leaving the Spokane, the route enters the Great Plain of the 

 Columbia, a table-land stretching from the Cceur d'Alene to the 

 Cascade mountains, a distance of 200 miles. Its central and 

 western portions are of trap formation, and are described on the 

 map as sandy, rocky, and sterile. Its summit, 800 feet above 

 the Spokane river, is readily attained, the treeless plain is crossed 

 in a distance of 110 miles, and a suitable point for crossing the 

 Columbia river, 400 or 450 yards wide, reached, 140 miles dis- 

 tant from the Spokane. This point is about equally distant 

 from the navigable waters of the Pacific in Puget sound and in 

 the Columbia river. The whole intermediate space is occupied 

 by the Cascade mountains, with their secondary chains, spurs, 

 and high, broken table-lands, through which there are but two 

 passes reported practicable for a railroad — that of the Columbia 



