ROCKY MOUNTAIN PASSES. 
101 
in whose judgment and experience I place great confidence. The route will be long, in conse¬ 
quence of the curves of the river, and will involve curves of the minimum radius, numerous bridge 
crossings, considerable side-cutting, and high embankments on the prairie portions in consequence 
of the spring freshets. The rock in side-cuttings can be easily quarried. The greater portion 
of this route has been personally examined by me, and I am satisfied of its practicability, though 
at great expense. 
The divide of the Jocko, though five hundred and sixty feet above Hell Gate, is entirely 
practicable. To overcome the summit the approach may require a grade of fifty feet, and the 
descent a grade of sixty feet; both, however, for short distances, with heavy embankments and 
probably a lofty bridge. Farther down the valley is open and easy, and the grades do not 
exceed twenty feet. There are no short curvatures. Lieut. Donelson is of opinion that these 
grades may be reduced to forty-five and forty feet. 
The distance to Horse Plain from Hell Gate by the two routes is 136 miles by the Jocko, 
and 143 miles by the Bitter Root, giving seven miles in favor of the former route. It is probable 
that the greater amount of curvature on the Bitter Root would be at least as serious a difficulty 
as the greater grades of the Jocko. The cost of the Jocko will probably be some half a million 
of dollars less than that of the Bitter Root. 
It is probable that a better connexion than either of these could be made by leaving the 
Blackfoot trail some distance before entering the defile, passing over a low divide, and pursuing 
the valley of one or two streams which flow into Clark’s fork. One of these streams is probably 
a tributary of the Jocko river. Enough is known of the country through an exploration made 
by Mr. Tinkham, under the direction of Lieutenant Donelson, to make it probable that the 
grades will not exceed forty feet, and that the curves and expensive embankments, and sustaining 
walls of the defile ending in Hell Gate, and of the Bitter Root valley, and the high grades of the 
Jocko route, will thus be avoided. The route is indicated by dotted lines on the sketch, and 
should be carefully examined in subsequent surveys. By referring to Mr. Tinkham’s route, as 
shown on the map and explained in his report, it will be seen that he observed all but a few 
miles of both routes, and that the connexion is almost certain. 
I will observe, however, that the examinations of this mountain range, whilst they have been 
exceedingly satisfactory, and have established the practicability of a railroad route through them, 
are by no means complete. 
It is not doubted there are other passes in this portion of the Rocky mountain range even better 
than those explored; they are indicated by the general depression of the mountain range, with the 
greater frequency of the streams stretching out to meet each other from the opposite slopes of the 
mountains; and I consider it important that, in future operations, a whole season should be 
directed to their thorough examination, and that instrumental surveys should be made of the 
pass found to be the most practicable. 
In the construction of the road through the Rocky mountains, there will be a scarcity of wood 
and water in the approach from Milk river, which can be remedied by bringing water in aque¬ 
ducts from Grizzly Bear lake, and wood from the Rocky mountains, which furnish an inexhaust¬ 
ible supply. 
