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

GEOLOGY.
great distance from the mass of the mountain, which thus appears furrowed by rugged and plecipitous canons. Each spur, as far as examined, presented rocks similar to tho(se already
described, the trend also being northwest and southeast, and the dip about forty degrees. The
rocks appeared in jagged points al] over the mountain, and no soil or vegetation could be seen.
Large beds of limestone were, however, observed, much thicker and more extensive than the
exposures seen before. It rests in inclined beds, conformably with the gneiss or mica slate, and
is belted or marked by bands and lines in the same direction. Thin seams or veins of granite
VIEW FROM CAMP NEAR THE DESERT.
and of quartz were also seen in parallel layers. Crystallizations of hornblende and other
minerals were observed at the line of junction of the beds with the granitic masses. This limestone is granular-and crystalline, and is more or less blue, and is not as white and coarsely
crystalline as the metamorphic limestones of New Jersey and New York.
COLORADO DESERT.
The ground over which we passed was gravelly and sandy. The sand was coarse, for all the
finer particles had been removed by the wind. A range of hills, at the base of the mountains
on the left, distant about ten miles, appeared to be composed entirely of sand, its surface being
drifted into ridges.
eot Spring.-After travelling about seven and a half miles over these long and barren slopes,
we saw a green spot in the distance, and soon came to two large springs of water rising in the
bare plain, not far from the foot of the mountain. (See map.) One of these springs is warm,
94