ROUTE NEAR THE FORTY-SEVENTH AND FORTY-NINTH PARALLELS. 53 
the low elevation of the former. That the winter climate is severely cold on the prairies 
between Fort Benton and the mountains, and in the Rocky mountain passes, is inferrible 
from the reports of Mr. Tinkham and Lieutenant Grover. That the cold is excessive on 
the prairie over the whole route is evident, from the meteorological information contained in 
the report." Mr. Tinkham, after crossing the summit of the Marias Pass, (latitude 48° 30/ 
about,) found, on the 20th of October, at an elevation of 5,600 feet, (800 feet higher than the 
proposed tunnel in Lewis and Clark’s Pass,) the snow-banks ofthe previous winter still resting 
on the borders of the shaded ponds or small lakes; and in the prairies, twelve miles from 
the summit, he found four inches of snow. On the route to Fort Benton, (from this pass,) 
between the 20th and 27th of October, distance 136 miles, the thermometer was once or twice 
as low as 3° Fahrenheit. 
Lieutenant Grover crossed the Rocky mountains through Cadotte’s Pass, in January of 
1854, and while in the pass the thermometer descended as low as 21°, 19°, 15°, below zero of 
Fahrenheit. 
The meteorological observations of the Medical department of the army, furnished me from 
the Surgeon General’s office, form the data, in addition to those given in Governor Stevens’s 
report, for the deductions drawn respecting the amount of snow, rain, temperature, &c. 
GENERAL REMARKS. 
The two principal favorable characteristics of the northern route, are its low profile and 
low grades; the prairies extending in this latitude from the Mississippi to the base of the 
mountains, fifteen or twenty miles from the summit, in about longitude 112° and 113°, a 
distance by the railroad route of 1,000 miles. Its proximity to, and connexion with the Mis- 
souri and Columbia rivers and their principal tributaries, is also favorable to its construction. 
The road leaves the Mississippi river, at Little Falls, at an elevation above the sea of 
about 1,100 feet. Between Mouse and Missouri rivers it has attained an elevation of more than 
2,000 feet. Its general elevation on the Missouri and Milk rivers is 2,200 feet. Leaving Milk 
river, it crosses the high prairies towards Lewis and Clark’s and Cadotte’s Passes; at the 
distance of 100 miles on the travelled, and 130 on the railroad location from these passes, 
the elevation is about 3,000 feet. Upon entering the passes it is about 4,600 feet, the summits 
being respectively 6,300 and 6,044; and the proposed tunnels at elevations of 5,300 and 5,000 
feet respectively. : 
After passing the summit we descend to the elevation of 3,000 feet, at about 100 miles west 
of it, by following the valley of the Bitter Root, and 130 miles west of it, following the 
Jocko, making the whole distance on the railroad route, exceeding an elevation of 3,000 feet, 
to be about 260 miles. At the junction-of the Bitter Root and Flathead rivers, which forms 
the commencement of Clark’s fork, the elevation is about 2,500 feet, and at Pend d’Oreille 
lake about 1,600 feet. In crossing the dividing ridge between Clark’s fork and the Spokane 
river, and the Great Plain of Columbia, between the Spokane and Columbia, the elevation 
attained is about 2,400 feet. If the mountain district be considered to extend from Sun 
river to Pend d’Oreille lake, the route runs through 310 miles of it; if to the Spokane river, 
about 400 miles. 
The sum of the ascents in crossing main divides or ridges going from Fort Vancouver, 
elevation 0, to St. Paul, elevation 828 feet, is about 9,500 feet; from Seattle, on Puget sound, to 
St. Paul, the sum would be 10,000 feet. 
The descents, going west, would be, respectively, above 8,700 and 9,200 feet. 
Applying Latrobe and Knight’s rule for equating grades, the effect of these ascents 
and descents, on the working of the road, would be equivalent to 343 miles in the first instance, 
and 362 in the other. 
