Reports of explorations and surveys, to ascertain the most practicable and economical route for a railroad from the Mississippi River to the Pacific Ocean: Vol. 5, Pt. 2

GRANITE-SLOPE OF THE GREAT BASIN-VEGETATION.
we reached Johnson's river, a powerful and rapidly flowing mountain stream, a few yards wide.
The water was very pure and cold. The channel or bed of the river was filled with rounded
blocks of granite, syenite, and metamorphic rocks, probably all derived from the ridges among
which the stream flows. No basaltic or trappean rock was seen. Some of the syenites were
however, very compact and fine-grained. We encamped on the eastern side of the stream;
nearly opposite us, there were outcrops of granite, light colored, and decomposing rapidly. It
was found to be traversed by great veins of quartz and feldspar. Mr. Ridley, who had
travelled among the lower ridges between our last camp and this river, brought me several
specimens of agate and carnelian which he had picked up.
Johnson's river to the Aojave, October 18.- A trial was made of the sand along the margin of
the stream for gold. Several pans-full were washed out without finding the color. Black sand
and garnets were very abundant. The sand and gravel were, however, not taken from the bedrock; this could not be reached in the short time before starting from camp in the morning.
No slate rocks, such as usually bear gold, were seen. Mr. Smith obtained a large peice of white
limestone from the top of the hill on the right of camp. This hill and others in the vicinity
appeared to be formed of sedimentary rocks in horizontal strata, probably Tertiary.
The route of the Expeditiorn from this river was in a direction a little south of east, over the
broad slope of the Great Basin, being below the foot-hills of the mountains, and yet only a few
miles distant from them. The slope was broad and gentle, extending for nearly fifteen miles
from the mountains without its surface being broken by a ridge or diversified by trees of any
magnitude. When looking in advance, the inclination was very evident, and opposite the Cajon
Pass there seemed to be a swell of the ground, so that the outline of the descent was brought
very distinctly into view; its inclination was approximately obtained by the clinometer, and the
angle was found to be between five and seven degrees. Near the mountains the surface was
uneven, and furrowed by the channels of streams, then entirely dry; but lower down, all these
channels were obliterated, or became so shallow as not to offer any impediment to the passage
of the wagons. In the banks of these dry streams the nature of the materials composing the
slope was fully exposed, and generally appeared unconsolidated and rudely stratified, in many
places much resembling ordinary till or drift.
The higher parts of the slope are covered with a thin growth of the yucca, or Spanish bayonet
tree, occupying a belt three or four miles in width. They are interspersed with cedars, which
grow to be large shrubs or bushes, and do not form high branching trees. The trunks are,
however, quite large-some being over a foot in diameter, and the limbs spread over a wide
surface, but the height rarely exceeds twelve or fifteen feet. Sage bushes, (Artemisias,) and many
small thorny shrubs, grew thickly together in many places between the cedars. Bunch-grass was
also common, but was entirely brown and dry.
About sunset a small running stream was unexpectedly found. It was not bordered by high
banks, nor were there any trees on its borders. It seemed to be a temporary flow from the
mountains. After resting at this point until late in the evening, the journey was resumed by
moonlight. The air was slightly charged with moisture, and at first the stars were but dimly
seen. The course lay, as before, over the unbroken slope parallel with the mountains. The
party in advance lighted up their trail at intervals, by piling dry shrubs and bunch-grass
against the windward sides of the cedar bushes and igniting them. They produced broad sheets
of flame, and made excellent beacon fires.- As the day began to dawn in the east, and the outlines of the mountains beyond the Mojave river became visible, we reached the old Spanish trail,
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