CHAPTER XII. 
Resumé of the Line from the Base of the Mountains to Puget Sound. 
As before observed, the immense prairies, the marked characteristics of the country west of 
the Mississippi, stretch to the very base of the Rocky mountains, and to this limit a railroad will 
have no greater obstacles to overcome than the passage of prairie elevations, and the crossing 
of a few small rivers. It is a singular truth, that while the whole mountain district has a clear 
breadth by a direct line of 200 miles, the eastern prairies north of the Missouri make up to 
within fifteen or twenty miles of the summit ridge; and on leaving the prairies and tracing up the 
several small streams which head in the mountains on the eastern side, one finds himself not 
only thus suddenly thrown into the midst of the mountains, but that he has hardly crossed their 
boundary before he has commenced their descent towards the Pacific. 
The plains at the entrance to the mountain passes have an elevation of about 4,700 feet above 
the sea, or are about six hundred feet lower than the tunnel proposed for passing the dividing 
ridge, and the grade line connecting the two is along the hill-sides at the sources of the tribu- 
taries of Beaver creek. The country at this short interval is a good deal broken; the culvert 
crossings of the several small brooks will be expensive, and the excavations will frequently be 
rock. 
It is estimated that a grade of forty feet can be obtained from the plains to the tunnel. 
The Rocky mountain divide, at Lewis and Clark’s Pass, is a narrow, sharp ridge, whose 
extreme elevation is 6,323 feet above the sea, and whose opposite bases, over 1,000 feet below 
the summit, are two and a quarter miles apart. The passage of this summit is by a tunnel 
through rock two and a quarter miles long, and at an elevation of 5,300 feet above the sea. 
The western descent is made with a forty to fifty feet grade. In common with Cadotte’s Pass, 
Lewis and Clark’s Pass opens into Blackfoot river, and the routes crossing the mountains by 
the two passes unite soon after, gaining the river valley on the west side. 
Blackfoot river has a generally narrow and wooded valley, the enclosing wooded hills some- 
times encroaching upon the river, and sometimes widening and discovering easy-sloping, small, 
and fertile prairies. The stream itself, from a mountain brook at the summit, ninety-three miles 
lower down, in the vicinity of Hell Gate, has a width of two hundred feet, and a depth of 
three feet, flowing over a clear rocky bed. Its bottom is wooded, and the bitter cotton-wood 
is found mingled with the pines and the different evergreens which make up the exclusive 
growth of the higher grounds. The valley has an average descent of twenty-two fect per mile. 
The bottom-lands of the valley of Jocko river, along whose edge the railroad line is marked, 
are not generally wooded. The valley from the summit drops down very suddenly towards 
Clark’s fork, facing the line to the wooded hills skirting the eastern side of the valley, and great 
care will be necessary, in locating the line, to obtain suitable grades. The descent on the eastern 
side of the valley, which appears most promising, involves the crossing of the main branch of 
Jocko river at a considerable elevation. A descent on the western side would avoid this, and 
may be practicable. 
Clark’s fork, where the line first enters its valley, is from one hundred and fifty to two hundred 
yards wide—a clear, rapid river, and is rarely fordable. With the exception of the occasional 
small prairies, serving as camping grounds, and noted on the maps, its valley throughout is 
heavily timbered, mainly with the pine; cedars of great size are met with in some parts of the 
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