42 ROUTE NEAR THE FORTY-SEVENTH AND FORTY-NINTH PARALLELS. 
Root rivers; the former rising in about latitude 48° 30’, and running south, and the latter 
rising in about latitude 45° 30’, and running north. As these two streams approach each 
other a spur from the Rocky mountains turns them towards the west. Their junction forms 
Clark’s fork of the Columbia, a clear, rapid river, from 150 to 200 yards wide, rarely fordable, 
which has forced a passage through the Bitter Root mountains; this pass was adopted for the 
railroad route. 
Seven passes in the Rocky mountains were examined ; they lie between latitude 48° 30’ and 
latitude 45° 30’. 
Beginning at the north, in about latitude 48° 30/, is the Maria’s Pass, leading from the 
Maria’s river to the Flathead river. It is not desirable in direction, unless a route leading 
westward be found north of Clark’s fork. The tunnel, at its summit, would be at an elevation 
of 8,000 or 8,500 feet; about the limit of perpetual snow in that latitude. On the west, the 
fall in seventeen miles would be 2,170 feet. The great severity of the climate would of itself 
render this pass almost impracticable. About the 20th of October, Mr. Tinkham found the 
snow-banks of the previous winter still lying upon the shaded borders of the small lakes or 
ponds on the eastern slopes at an elevation of about 5,600 feet. The instruments used by Mr. 
Tinkham were a barometer and pocket-compass. 
The next pass is that of Lewis and Clark, connecting the head-waters of Dearborn and Black- 
foot rivers—the former a tributary of the Missouri, the latter of the St. Mary’s. The summit 
ridge has an elevation of 6,323 feet, which must be pierced by a tunnel two and a half miles 
long, through rock, at an elevation of 5,300 feet; grades of approach from the east forty feet 
to the mile, and of descent to the valley of Blackfoot river, ‘‘it is believed,’ will not exceed 
fifty feet per mile. 
The examination of this pass was made by Mr. Lander; his instruments were a barometer 
and pocket-compass. He abandoned the examination (the reasons for it are not, to my appre- 
hension, contained in the extracts from his report) seven and a half miles west of the summit, 
and four and a half miles before reaching the route of the main party that entered the valley 
of Blackfoot river by Cadotte’s Pass. The connexion of Lewis and Clark’s Pass with the 
valley of the Blackfoot river has not, then, been made, though ‘¢ believed practicable at grades 
not exceeding fifty feet per mile.’’ This pass should be gone over instrumentally before its 
practicability can be considered demoustrated, Tt has been adopted in the railroad estimate, 
and is probably practicable. 
The next pass is Cadotte’s, connecting a tributary of Dearborn river with a tributary of the 
Blackfoot river. The approach to this pass is practicable, though difficult, owing to the 
numerous deep ravines of the tributaries of Beaver creek, a northern branch of Dearborn river, 
over which the road must cross in approaching the pass from Sun river. The summit of the 
pass has an elevation of 6,044 feet; will require a tunnel 4} miles long (fifty per cent. of cutting 
in clay slate,) at an elevation of 5,000 feet, with grades of sixty feet approaching from the 
east, and forty feet per mile from the west. The pass itself is difficult. 
The main train of the exploring party passed over this route, the instruments used being 
a barometer, odometer, and Schmalkalder compass. It follows the valley of Blackfoot river, 
generally narrow and wooded, to its junction with the Hell-Gate, a distance from the summit 
of ninety-three miles. For twenty miles before this junction there is a narrow gorge ending in 
Hell-Gate. From the narrowness of the valley and winding of the stream, it will be necessary 
to cross frequently from side to side, and the bridging will be expensive from the absence of 
stone suitable for building material, the nearest point of supply known being in Flathead River 
valley, seventy miles distant from Hell-Gate. The grades will vary from thirty-five to forty- 
five feet per mile. 
The Blackfoot river joins the Hell-Gate river just before the latter makes the passage of the 
gorge from which it derives its name, the Hell-Gate river itself being a tributary of the St. 
Mary’s. At the head of the Liddle Blackfoot (another tributary of the Hell-Gate, coming from 
