110 
GEOLOGY. 
there were no buckets or conveniences for drawing the water. This water was found to he turbid, 
and slightly brackish. The country around the camp was peculiarly dreary and desert-like. 
Quantities of skeletons of cattle and mules, with loose hones and skulls, were lying about in 
confusion. Near the well were several carcases hut partly decomposed, and others completely 
dried up, so that the skeleton was held firmly together by the hard and tightly-stretched hide. 
The clay surface upon which these remains were distributed was perfectly barren and overlaid 
by a thin coat of dry sand, which the wind drifted into little mounds, and moved about with a 
low, rustling, and mournful sound. 
WELL IN THE DESERT—ALAMO MOCIIO. 
The hank above the well, as represented in the engraving, appears like a wall of stone, but 
it is nothing more than an indurated clay, of a reddish and gray color, very fine and regularly 
stratified in horizontal layers. A specimen of the clay of a bluish-gray color was preserved, 
(No. 162 of the catalogue.) No shells or fossils were observed. 
December 6 .—Alamo Mocho to Cook's Well, 22 miles .—The trail from the Alamo well winds 
along on the top of the hank. The surface is slightly undulating, and is overspread with con¬ 
siderable accumulations of gravel and pebbles. We passed many slight mounds, ten or fifteen 
feet high, upon which large shrubs of Larrea Mexicana were firmly rooted, and had evidently 
been growing in the same position for many years. At a short distance, these mounds looked 
like sand-hills ; and it is often the case that a thin layer of blown sand spreads over or around 
them. They are also composed essentially of sand ; but the grains appear to be hound together 
with fine cl#y or dust, so that they resist the winds and are not shifted about. 
Eleven and a half miles beyond the Alamo well we crossed the point of a thin layer ot 
blown sand that had accumulated about the roots of the larrea, which grew abundantly in that 
vicinity. 
There was little to vary the monotony of the scene on this broad Desert, except the gradual 
changes in the appearance of distant mountains as we neared or receded from them. Signal 
mountain was now behind us, and gradually sunk below the plain; while on the left the moun¬ 
tains loomed up one range after another in long blue lines. Another object made its appear¬ 
ance in advance : the blue summit of a mountain rose just above the horizon, and became higher 
and higher as we advanced. This was Pilot Knob, an isolated elevation on the banks of the 
Colorado. 
