ROUBIDEAU'S PASS. 41. 
regard for his health compelled us reluctantly to part with him here, hoping that the’ pure air and 
quiet life of New Mexico would restore him to bealth. 
August 23.—W e were detained in making necessary repairs, and in obtaining supplies at Fort 
Massachusetts, until this morning, when we took leave of the officers of the post, from whom we 
had received much courteous hospitality ; and, following down Utah creek for three miles and a 
half, crossed it, and passed along the base of the gravelly hills which lie directly at the foot of the 
Sierra Blanca, southwest and opposite the sharpest peak of which we encamped, at White Mount- 
ain spring, seven miles from Utah creek, and, in a direct line over the gravel hills, not more than 
that from Fort Massachusetts. These gravel hills are a confused set of elevations from fifty to 
one hundred feet in height, resulting from the washing away of a former deposit and the crumb- 
ling of the higher mountain masses. The mountain torrents have washed among them deep 
channels, and occasional dykes, like vertical walls laid up in regular masses many feet thick, 
are left exposed. These hills are covered with branching cedars and pines, seldom exceeding 
twenty feet in height. A few wild hops were observed growing luxuriantly at the crossing of 
Utah creek. r 
August 24.—Following the base of the Sierra Blanca on our right, with the broad valley of 
San Luis on our left, we encamped, after travelling fourteen miles, on a small stream from the 
mountain, which soon sinks in the plain. The grass along our path was scattered, and'we expe- 
rienced considerable difficulty in driving over the thick masses of sage which cover almost the 
entire surface of this immense valley. We were here nearly opposite to Roubideau's or Musca 
Pass. Captain Gunnison immediately proceeded to examine it. It was found impracticable to 
ascend it with horses, in consequence of one of those great mountain torrents, to which all mount- 
ain countries are subject, having swept down it, depositing trees and rocks in every direction, and 
tearing the bed of the creek, over which two light wagons crossing from the Greenhorn settle- 
ment to Taos had descended but a few days before, into holes and gullies ten and twelve feet 
in depth. For two hours the party toiled up the cañon, sometimes on one side of the creek 
(which is known as Musca or Fly creek) and then on the other, to the summit, through the upper 
opening of which they could look down upon the San Luis valley. _The course of this ravine 
from the summit is due west for two and a half miles; then nortb, 80? west, into the valley. 
It is 100 feet wide at bottom, with points of the rocky sides jutting into it, making the bed quite 
crooked. The sides are about 500 feet high, rocky and precipitous, but can be ascended by a 
footman from the stream at the bottom of the ravine as easily as most lofiy mountains can be 
climbed. The rocks of this pass are chiefly a coarse altered mica slate. The elevation of our 
present camp above the sea is 7,638 feet, and the difference of level between it and the base of 
the Sierra Blanca, 6.25 miles distant, 518 feet. From this point to the foot of the pass where 
it opens into the valley of San Luis, and thence to its summit, there is, unfortunately, a want of 
clearness in the record of the estimated distances from point to point where observations were 
made for differences of level. I have therefore taken the largest possible distances which could 
intervene between these points, presenting the pass in its most favorable aspect. By the direct 
path which we followed, this distance, between the foot-hills of the mountain and the narrow 
mouth of the pass, is 1.60 mile—the ascent being 450 feet, or a little over 281 feet per mile. 
But as these foot-hills are open rolling slopes, the pass could be approached by a much longer 
path from the south, distributing this elevation over several miles, bringing the grade for a rail- 
road within 100 feet to the mile. But above this point this pass is entirely impracticable for 
a railroad, and but little better for a wagon road, the ascent being in the next mile and a quarter, 
373 feet, and in the following seven-tenths of a mile, 377 feet, while in the succeeding three- 
fourths of a mile, to the summit of the pass, it is 416 feet; the whole difference of level 
from the mouth of the ravine to its summit, 2.70 miles, being 1,166 feet, the summit of the 
pass being 9,772 feet above the sea. No apparent obstacle presents itself from the summit 
to descending with facility from this pass to the Huerfano river to the north and east; but 
6g 
