ROUTE FROM THE GREAT BASIN TO MISSOURI RIVER. 
37 
lion of Pacific railroads only differ from those of minor lines as the hroad divisions of a continent 
differ from the limited sections of the county and the State, and as the choice of routes is 
affected by the claims and contingencies of construction, brought forward by the extreme 
length of line to he traversed, in the wear of the road during deferred connexion of termini. 
The inclinations of gradients are affected by the character and length of the approach, as 
much (in general terms only) as by the elevation of the summit to he overcome. 
A line which reaches, by the long inclined surface of the Platte valley and the Sweetwater, 
the level plains of the South Pass, and thence, without surrendering height accomplished, 
passes over the gradual slope toward the west of the valley of the Snake, and thence, by the 
low pass of the Pannack, reaches the plains of the Great Basin, necessarily avoids the steep 
grades induced by a descent into the great valley of the Colorado, (see route 39th parallel, and 
in less degree 42d parallel,) and the subsequent rise over and descent from the Wahsatch 
mountains, to the plains of the Great Basin. The intermediate country, broken by the passage 
of water, is avoided by detour. 
Therefore, were this surface of the swamps and sand-plains of the Great South Pass not at so 
great an elevation above the sea as to place it near the regions of perpetual snows, the argument 
would he unanswerable regarding its selection in reference to the extension of a preliminary 
road. This is an evident conclusion, because the engineering requisition to be answered is, the 
finding of a continued line of flat or slightly inclined surface, over which a rail may he 
extended to the Pacific within seven years. 
But if the preliminary road traverse the plateau of the South Pass, and the long flat line of 
country beyond it, fully 7,400 feet above the sea, it would he exposed to the inevitable dangers 
and embarrassments of this elevated region, regarding snow and frosts. 
To expedite preliminary arrangements, it has been proposed to use the natural surface (where 
of gravel or sand substrata) without grading. 
Over the South Pass this could only take place during half the year. But in a more deferred 
mode of extension, the facile line of approach to the South Pass will permit, by the adoption of 
steeper gradients, of the erection of an embankment road-bed, which will in some measure 
guard against the. obstacle of snow. Even an open structure, through which snow would drift, 
and over which trains could pass, might thus he adopted, or (with the surface road) a covered 
way under which trains could make transit. But in reference to snow, the elevation of the 
summits of the broken and undulating surface in the vicinity of the Bridger’s Pass, are hut 
slightly below that of the flat plains of the South Pass. The excavation of cuttings and the 
erection of culverts and bridges for the passage of water, would there unquestionably postpone 
communication, and in a measure prevent the earliest use of the carrying road. Again, every 
railroad employee knows the difference between a cutting and an open road, regarding embar¬ 
rassments from snow. The mountaineers of this section state that they can travel over the 
plains of the South Pass in winters, when the gorges of the more southern Bridger’s Pass 
line are filled with snow and impracticable of passage. 
Early communication is the desideratum, and this is resolved to the most rapid extension of 
a preliminary railroad. Therefore, in view of the extension of a similar line as a winter road 
over the sand-plains of the extreme southern frontier route to California, I should give the pre¬ 
ference to the route by the detour of the South Pass. Notwithstanding some increase of dis¬ 
tance and of the cost of rails, it would probably he less expensive than the other, and would 
sooner reach the plains of Snake river and the Great Basin, and carry supplies for a working 
section across those plains. 
But returning to the engineering presumption first submitted, we might more reasonably 
infer that, from the difficulty of arriving at a conclusion at the present time, this question of 
choice between two lines of a route should he left open. It should he determined by future 
examinations during the construction of that first section of the line of the emigrant road, which 
is the grand approach to both the South and Bridger’s Passes of the mountains ; although, to 
