ROCKY MOUNTAIN PASSES. 
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narrow and somewhat tortuous, will admit, however, of a railroad at a practicable grade—the 
eastern one to within from two and a half to three and a half miles of the lake whence the 
stream has its source; the western valley three and a half to four and a half miles from its 
lake. These two points are six to eight miles apart, and differ in level some 300 to 500 feet. 
Between them the valleys rise rapidly, attaining at the two lakes an elevation respectively of 
2,000 and 1,300 feet above the western, and 1,500 and 800 above the eastern base. Thus a 
tunnel having an inclination of 37.5 to 83.3 feet, and six to eight miles long, is the essential con¬ 
dition to a road by this route. 
The route by the Coeur d’Alene mission is exceedingly direct, both in its own course and in its 
connexion with the Blackfoot and Hell Gate trails. If practicable, it would abridge distance 
about seventy miles, equivalent to the cost of a tunnel of about the probable length of the tunnel 
required on the Coeur d’Alene route. The cost of the tunnel, supposing it to be seven miles long, 
would be about $5,000,000. It is in limestone entirely, and easily worked. The saving in the 
length of the road would be, say 70 miles, at $70,000, or in round numbers $5,000,000. It was 
unfortunate that a barometrical profile could not be taken on this route in consequence of the 
want of instruments ; but Mr. Stanley, an excellent judge of distances and heights, made esti¬ 
mates which I am satisfied, from my own personal observation, will prove good approximations. 
There is a good wagon-road from the mission to Wallah-Wallah, indicated on the map, and it is 
believed no difficulty would exist in connecting this route, south of the Coeur d’Alene lake, 
either with the Columbia river or Snoqualme Pass route. 
The valley of Clark’s fork, however, affords an excellent railroad line presenting no special 
obstacles; and the question now is, to determine which pass of the Rocky mountains shall be 
made use of in passing from the plateau between the Milk and Missouri rivers to Clark’s fork. 
Nine passes have been explored in the Rocky mountains, beginning twenty or thirty miles 
below the 49th parallel, and extending southwardly three hundred and four miles in latitude, to 
the most southern pass explored at the source of Jefferson fork. From this pass to Fort 
Hall, the extreme southern limit of the exploration, the distance in latitude is eighty miles. The 
northern pass, termed the Marias Pass, where a tributary of Clark’s fork has fts spring near 
the source of the Marias river—elevation 7,669 feet; a pass at the head of Beaver creek on the 
east, and a tributary of Blackfoot fork on the west—elevation 6,323 feet: this is the pass of Lewis 
and Clark; Cadotte’s Pass, named from one of our hunters, who used the pass some two years since, 
forming the headwaters of Dearborn river and Blackfoot fork, 6,044 feet high ; a pass at the head 
of the north branch of the Little Blackfoot fork on the west, and a stream making into the Missouri 
on the east—elevation 6,283 feet; a pass at the south branch of the Little Blackfoot river ; a 
pass at the head of the Hell Gate river; one from the East fork of the St. Mary’s river to the 
Wisdom fork of Jefferson river; and, finally, a pass from the East fork of St. Mary’s or Bitter 
Root river to the Wisdom fork of Jefferson river. 
Marias Pass, the extreme northerly one of all, is the passage over the mountains by a tributary 
of Marias river on the east, and of Flathead river on the west, the wooded valley of which leads 
down to the open, wide valley, where is Flathead lake. The branch of Marias river is a mere 
brook where it leaves the limits of the mountain and passes to the smooth prairies, only nine or 
ten miles from its source, and the rocky wall-like divide which abruptly terminates its valley. 
This divide, when crossed at its highest point by the trail, is 7,600 feet above the sea; and its 
height, where seemed to be the most favorable opportunity of tunnelling, is apparently 500 to 
1,000 feet higher. A tunnel of two and a half miles (an uncertain estimate from the manner in 
which the divide was crossed) would probably reduce the elevation so far as it is practicable to 
do so by tunnelling, the mountain being pierced at an elevation of 5,450 feet; but the rapid 
descent of the tributary of Flathead river, to which we pass on the west lor the first seventeen 
miles, in which distance it falls 2,170 feet below the level assigned to the tunnel, is so objection¬ 
able that this route is not likely to come into competition with the passes farther south. On the 
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