COOCHETOPA PASS AND TUNNEL. 85 
examined and deemed entirely impracticable for a railroad; the grade to the west being, for 
the first 1.25 mile, at the foot of the ravine, 298 feet to the mile, and 490 feet to the mile for the 
succeeding seven-tenths of a mile, and 554 feet per mile for the last three-fourths of a mile at the 
summit, with a broad slope extending thence north and east to the Huerfano river. 
Continuing up the valley of San Luis, the grades from camp to camp are, respectively, as follows: 
An ascent of nine feet eight inches for 9.78 miles; a descent of 24 feet per mile for 9.06 miles; 
an ascent of 8.7 feet per mile for 11.72 miles; a descent of 9.5 feet for 5.96 miles, with an ascent 
of but 19 feet in 15.20 miles, to the camp on Sahwatch creek at its entrance into the valley of 
San Luis. 
Gunnison's Pass lies immediately to the northwest of the Sierra Mojada, between the head- 
waters of the Rio Grande del Norte, in-this direction, and the Puncha creek, an affluent of the 
Arkansas above its cation. Captain Gunnison deemed it practicable for a railroad which should 
ascend the Arkansas river through its cañon, and across the plains which lie above it, ascend- 
ing a branch of the Puncha creek to the summit of the pass, and descending through Homans' 
park to the valley of San Luis. The altitude of this pass, 8,603 feet, and the grades in its 
vicinity, are derived from aneroid observations, referred to our camp of August 27th, 28th, and 
29th, in the San Luis valley; but are not relied upon with great confidence for actual altitudes 
above the sea, although the relative differences of level indicated by them are more satisfactory. 
They give grades of 185.5 feet per mile for four miles, ascending the pass from the east; then 
228 feet per mile for one mile and a half, followed by a grade of 113 feet to the mile for three- 
fourths of a mile, to the summit. Descending to the west, the difference of level is 56 feet per 
mile for six miles; then 68 feet to the mile for three miles, to the centre of Homans' park, from 
which a road can be carried in any direction across the San Luis valley. 
The approach to the Coochetopa Pass, by the Sahwatch creek, opens very favorably for the 
construction of a railroad. The mouth of the valley of this stream is from five to seven miles in 
width, but soon narrows in ascending it to a few hundred yards, and seldom again exceeds half a 
mile in width to its head. For twelve miles we ascended slightly over 39 feet to the mile; 
and for the following fifteen miles nearly 61 feet to the mile—having, during the day, left 
the Sahwatch creek and ascended its branches, occasionally overhung by walls of igneous rocks, 
giving this part of the pass a defile character. But, in the construction of a railroad, it will be 
necessary to carry it on the side of the ravine considerably above the stream, gaining an elevation 
of at least 200 feet at the fifteen-mile station referred to; which, from the formation of the hills, 
must be done upon the last few miles below that point, the elevation of which is 8,960 feet above 
the sea, while the summit of the pass, 3.83 miles distant, is 10,032 feet, which will require for 
its passage a grade of 124 feet per mile for 3.07 miles above this point, followed by a tunnel, 
entering the mountain from the east three-fourths of a mile below the summit, diminishing the 
elevation to be overcome by 490 feet, and terminating to the west, with a deep approach, (near 
our camp of September 2d), 1.33 mile below the summit—the length of the tunnel, which must 
be cut entirely in rock, including the approach, being two miles. 
The altitude above the sea, ten thousand feet, indicated by our barometers in this pass, is that 
to which all the depressions in the vicinity will approximate. It is possible, however, that the 
summit of the Carnero Pass, just south of the Coochetopa, may be more easily passed by a rail- 
road than the latter; but this can only be determined by a minute survey. In any future explo- 
ration, examination should be made for a passage in these mountains by ascending any small 
stream entering Homans’ park from the northwest, and passing over to the head of the Cooche- 
topa creek, and thence descending to Grand river—the formation of the country indicating a 
pass in that direction. 
Below our station, 1.33 mile west of the summit of the Coochetopa Pass, the grade again 
becomes practicable, being, by the valley of Pass creek for 2.24 miles, 105 feet to the mile; 
68 feet to the mile for the next 2.15 miles; 93 feet per mile for the following 2.05 miles; 
