36 ROUTE FROM THE GREAT BASIN TO MISSOURIRI ER. 
freshets of Snake river, involving some preparation of rough surface to use best 
route of descent to Boisé, but with long stretches of level gravel plains $6,000,000 
From Fort Boisé to the Great Basin, including passage of the Pannack, by practica- 
ble detour—say five hundred (500) miles, over gravel plateau 9,000,000 
For general approximation, say eleven hundred (1,100) miles of road from Seattle, 
on Puget Sound, to the plains of the Great Basin 26,775,000 
As connected with a railroad line to California, by the South Pass and valleys of the Snake 
and Pannack rivers, the branch road would be subject to a reduction, in cost, of about four mil- 
lions of dollars. . 
In the above estimates an addition of fifty (50) miles, at average cost, has been made for 
contingencies and probable deflections in locating a preliminary road. 
CONTINUATION OF RECONNAISSANCE TO MISSOURI RIVER. 
The route just described is, as heretofore stated, the northern branch of a forked route, the 
main stem of which extends from the plains of the Great Basin to Missouri river. The southern 
fork of this route, and the main trunk or stem, is termed, in the reports of the Pacific explora- 
tions, the route of the 42d parallel. "Two of the lines ofthe route of the 42d parallel respect- 
ively extend—the one through the South, the other through the Bridger’s Pass of the Rocky 
mountains I consider the choice between, or selection from, these two lines, the most important 
and interesting of the many engineering details connected with the adoption of the line of a 
central railroad to California. This is especially the case, if the selection is to be guided by a 
determination to reduce the whole question of a railroad to the Pacifie to the construction of 
such a sort of military railroad as shall reach the Pacific coast within seven (7) years. 
The statements of the Introduction to this Synopsis will now have their weight, and simplify 
the final engineering presumption of that paper—that Congress should hesitate to do more, at 
the present time, than aid the construction of those first sections of the Pacific railroad lines 
contiguous to the States ; aiding the first sections of routes of undulating surfaces, with refer- 
ence to the needs of civilization and way-transportation, if deemed constitutional, by land- 
grants; but aiding the two lines of plateau surface, extending over broad plains, with a view 
of the earliest practicable connexion of termini. 
The following reasons are offered for arriving at such definite conclusions in reference to the 
route of the 42d parallel: 
The first section of this route is the line of approach to both the South and Bridger's Passes 
of the Rocky mountains. 
The examinations of these passes have been confined to reconnaissances, and have not yet 
been verified by survey. 
By reference to the sketch, it will be seen that a dotted line is carried from the South Pass, 
in a northwesterly direction, to the head-waters of the Snake. This line (so far as examined) 
extends over a broad gravel plateau ; a flat sand-plain, interspersed with swamps and ponds 
of brackish water. The South Pass is nothing but an extended plain, slightly broken towards 
the south into an undulating country. It is the first break down of the Great Wind River 
mountains at the north, among which is a summit of over 12,000 feet above the sea. In this 
plain, and among these ponds and swamps, head the waters of the tributaries of the Grand 
Colorado, the Snake, and the Platte. The engineering rule—in seeking location over broad 
belts of surfaee between termini which extend at angles to the direction of great watercourses— 
is to skirtthe country in which they head, or to pass over the lower delta where they have de- 
posited, in broad terraces, the earth from the deep channels excavated by their flowage, rather 
than to adopt the intermediate region, broken by their transit.  Reconnaissances for the loca- 
