66 
GEOLOGY. 
sinks away in the sand, and there is nothing on the broad semi-desert slope to indicate its 
existence. 
We were greatly refreshed hy a hath in this beautiful stream, and a night’s rest on the clean, 
hard sand of its borders ; and on the morning of the 23d left for the entrance to Williamson’s 
Pass, taking the same trail that had been broken hy the wagons of our train a few days pre¬ 
viously. 
Copper ore .—About seven and a half miles beyond Johnson’s river, some small boulders, cov¬ 
ered hy greenish stains, were observed in a small, dry arroyo, which was apparently formed hy 
the washes during rains. It was soon ascertained that these stains were produced hy carbonate 
of copper, and I concluded to trace these fragments to their source. At the expense of being 
“late at camp,” the parent source was found in an isolated ridge of mica slate and granite 
about two hundred fe.'t high, and not far from the main ridges of the Sierra. The ore consists 
of iron and copper pyrites in a quartzose gangue, and has a direction nearly N. 75° E. The 
upper or outcropping portions are much decomposed, and stained hy oxyde of iron and carbonate 
of copper. 1 
Cottonwood creelc—Sandstone strata .—From the copper-ore locality, I passed along the foot¬ 
hills, and followed up the dry bed of a stream towards the mountains. It was evident that at 
certain seasons a very large body of water ran there, as the channel was strewed with large 
rounded masses of rock, which were mostly of granite, and were piled together in confusion. A 
grove of cottonwood trees was also visible some distance up the channel, and contrasted strongly 
with the brown and barren-looking hills on each side. On nearing this grove, indications of 
water were observed, and several deep pools were found at the base of an almost vertical wall of 
sandstone strata, which were inclined at a high angle, and surmounted hy layers of drift-sand 
and gravel, as shown in the accompanying figure. 
SANDSTONE STRATA OVERLAID BY DRIFT. 
It was evident that the water was much higher at certain seasons, and that it flowed with a 
strong current, it having worn caverns and deep hollows in the strata. These beds consisted 
principally of the debris of granite, and they were of a light color, with a shade of red. The 
materials were coarse, and no indications of organic remains were seen. 
This stream was afterwards named Cottonwood creelc, from the abundance of cottonwood near 
its sources. 
Leaving the valley of the creek, I crossed over two, rounded, sedimentary hills, and passed 
westward to another valley or dry ravine, which was supposed to lead to the new pass. Finding 
the track of the wagon, which had passed before me, I ascended this valley to the mountains, 
and rejoined the party. After climbing up steep ridges and canons in all directions, and not 
finding a place where the wagon could he taken over, we concluded that we had not ascended 
the right ravine, and were not at the pass which Lieutenant Williamson had found. We also 
ascertained by the barometers that we were at an altitude of over four thousand feet, which was 
much higher than Lieutenant Williamson had represented the summit of the new pass to be, he 
1 For a more particular description of this locality and the ore, see Chapter XX, on metals and ores. Specimens are in 
the collection Nos. 214, 215, 216. 
