276 LINE OF THE MARIAS PASS. 
[Hell Gate] valley does not exceed forty (40) feet per mile. The width of the valley is such 
that, by using curvature of twelve hundred (1,200) feet radius, at a few sudden changes of di- 
rection, the line need not make crossings of the stream; or should larger radii seem preferable, 
the character of the route may still be preserved, the river crossed at right angles to the current, 
and a reasonable length of straight line secured between the changes. The cost of all the bridg- 
ing upon the division will be excessive, from the scarcity of the proper material for masonry, the 
basaltic rock of the section being unfit for such structures. 
Should the line keep the northern bank of the river, an embankment formed of rock and earth 
by borrowing would avoid many deep ledge cuttings, and could be protected from the danger of 
sudden treshets by placing the weightier material upon the outer slope. For a portion of the 
distance through this valley, however, it will be necessary to make several crossings of the 
stream at high cost. The general grade down the Blackfoot [Hell Gate] fork of forty (40) feet 
per mile will probably be broken by the severe work, and lead to the location of steeper 
inclinations. 
The descent of the Bitter Root is very severe. The general grade of the river valley for that 
distance is not great, but the changes in level are abrupt; the valley extremely narrow and 
crooked; sharp curvature and steep gradients will be needed under any system of location, and, 
by the best mode of conquering these difficulties, the line will be extreme in cost and nearly 
impracticable. 
Many crossings of the stream are made; deep rock-cuttings occur, and all embankments must 
be thoroughly sustained against the effects of the rapid current and the danger of sudden freshets. 
From the junction of the Bitter Root and Clark’s fork to the crossing of Clark’s fork, below 
Lake Pend d’Oreille, the line assumes a more favorable character, and although still severe, may 
be readily adjusted to reasonable rate of curvature and grade. The crossing of the summit 
section between Lake Pend d’Oreille and the valley of the Spokane is very favorable, and can be 
made upon gradients of forty (40) feet per mile. 
All great difficulties of location upon the route, as delineated upon the sketch, cease at the 
valley of the Spokane, and choice can be made of several practicable lines to the great valley of 
the Columbia. 
19. Report or mR. A. w. TINKHAM, ASSISTANT ENGINEER, AS TO THE RAILROAD PRACTICABILITY 
OF THE LINE OF THE MARIAS PASS OF THE NORTHERN LITTLE BLACKFOOT TRAIL, AND OF THE 
SOUTHERN NEZ PERCES TRAIL. 
Wasuineton, D. C., July 19, 1854. 
Sir: On the 7th of October, 1853, in the valley of the St. Mary’s river, I received from you 
instructions to examine Marias Pass, to return to Fort Benton, and again from that post to travel 
westward, crossing the Rocky mountains by such pass as shall be expedient, and the Bitter Root 
mountain by the southern Nez Perces trail, to Wallah-Wallah. 
Three days later, having rested my animals, I left the last camping ground made by Lieuten- 
ant Donelson with the main train on Jocko river, and travelling northwardly, followed Jocko 
river to its mouth, and then journeyed up the valley of Flathead river. Until near Flathead 
lake, the valley of this river continues wide, grand, and bordered by partially-wooded hills. 
Most of this land is capable of occupation and settlement. The river is a fine, clear stream, one 
hundred to one hundred and fifty yards wide, occasionally fordable, swift current, and is esti- 
mated to have a descent of about ten feet per mile. About ten miles before reaching Flathead 
lake we leave the river and pass out of sight of it, and its issue from the lake could not be ascer- 
tained. The trail wound around the western shore of the lake. Its edge curves sharply and 
often, winding around the woody and rocky hills rising from the waters. The lake itself is a’ 
sheet of water of great beauty, some twenty-five miles long, and six or eight broad ; is adorned 
