272 ROUTE FROM FORT BENTON TO WALLAH-WALLAH. 
instances by high embankments. A bridge half a mile long would be necessary for crossing the 
valley of Pack river. 
I do not think there would be much difficulty in providing against the great freshets to which 
Clark’s fork is liable. As for the lake, so for this, fifteen is about the difference of level between 
high and low water marks. 
The tunnel at the Cabinet mountains would be through a formation of which fifty per cent. is 
rock, this being basaltic trap. 
As regards the subject of construction west of the Rocky mountain summit, it may be remarked 
that the line passes, in nearly its whole extent, through fine forests, which would furnish an abund- 
ance of pine, of cedar of fine quality, and of fir and larch. 
I saw no good stone for building. A locality on the Blackfoot fork not far from Hell Gate, ‘ Big 
Rock,” andthe mountains on the right of Clark’s fork for some distance below Thompson’s prairie, 
would, however, furnish a great abundance, which would answer for ordinary purposes. The 
prevailing rocks appeared to be a limestone, a quartz rock, somewhat resembling the gold-bearing 
quartz, and the basaltic trap. Mr. Tinkham mentioned that not far from the Hudson’s Bay Com- 
pany’s post, among the Flatheads, a great quantity of good limestone for building could be ob- 
tained. Not far from the lower end of the lake I think it would be advisable to mark the ¢rossing 
of Clark’s fork. 
Should it be desirable to carry the railroad by Fort Colville, I may here state that Lieutenant 
Arnold reports but one obstacle on the route he followed, and refers to a way by which that can 
be avoided. The transit from Clark’s fork to the Sponkane could be made with gradients of not 
more than twenty-five feet. It might be facilitated by making use of the valley of a small stream 
which empties into Clark’s fork at about twelve miles below the lake, and of a valley seen by us 
ten miles west of Clark’s fork, and which appeared to make into Coeur d’Alene prairie. A further 
examination is necessary to establish that the connexion could be made in this way. And if 
so made, a considerable deflection from the line of direction of the road would be required. 
The remainder of the distance to Wallah-Wallah could probably be accomplished with gra- 
dients of thirty-five feet to the summit between the Spokane and Lewis’s fork, of thirty feet from 
that summit to the crossing of the latter river, and of twenty feet thence to Wallah-Wallah. 
From the barren nature of this portion of country, the supplies for construction would have to 
come from the mountains to the east, and the valley of the Columbia to the west. From Fort 
Benton to Wallah-Wallah the distance is six hundred and fifty miles. In a direct line it is four 
hundred and six miles. 
The difference of level between the two points is about one thousand nine hundred feet. From 
the Rocky mountain summit to the Spokane river the location of the road can be more definitely 
decided upon than elsewhere on the route. Within these limits the most important curves are six 
which would occur in the first sixty miles west of the pass, and one that would be necessary not 
far above the junction of the Bitter Root river. These will be of from two to four thousand feet 
radius. ‘The great deflections from the direct line are, that to the south by way of the Blackfoot, 
and that to the north by way of Clark’s fork. The first could be reduced, if a good pass and 
route should be found at or near the head of the Jocko; the second, by pursuing a more direct 
route from the lower crossing of Clark’s fork to Wallah-Wallah. It will be seen, by examining 
the profile, that one hundred and twelve miles of the route—that is, from the summit between 
the ‘Teton and Sun rivers to our camp of September 24 and 25—are at an elevation of between 
four and five thousand two hundred feet above the sea. One hundred and twenty miles—that is, 
thirty-two miles from the high prairies opposite Fort Benton to the summit west of the Teton, 
and eighty-eight miles from the camp of September 24 to that of October 6—are at an elevation 
of between two thousand eight hundred and four thousand feet above the sea. Three hundred 
and forty-nine miles from the camp of October 6 to that of November 2, are at an elevation 
of between fifteen hundred and two thousand eight hundred feet; and sixty-nine miles from the 
