244 
GEOLOGY. 
are on the north side of the well, and several hundred yards north of the rocks forming the base 
of San Gorgono Mountain, so that a smooth and unobstructed passage-way is left between them 
and the rocks. This accumulation has a length of three or four miles, and extends in a nearly 
northwest and southeast direction. The range has a width of at least one quarter of a mile, 
near the Deep Well; but its northern margin was not seen. This sand is not so fine as that 
between the Alamo and the Colorado ; it, however, appears to have a similar chemical con¬ 
stitution. 
The observations already made on the contour and the movements of the sand-hills east of 
Alamo Well will apply to these drifts also ; but the circumstances under which they exist are 
quite different, in consequence of the absence of the terrace. The proximity of the bordering 
range of granite seems to exert an influence on the distribution of the sand at the well. It is 
probable that the violent lateral eddies, that are produced where the wind impinges upon the 
rocks, are sufficient to prevent the accumulation of the grains at the immediate base of the 
mountain. Appearances led me to conclude that an effect of this kind was produced ; the fact 
that the sand is always thrown to the lee side of an obstacle lends additional support to the 
conclusion. 
An immense body of sand has accumulated at the base of the mountains, on the north side of 
the Desert, nearly opposite Deep Well. It forms smooth, rounded hills, with wave-like surfaces. 
This accumulation is nearly opposite the slope of the Bernardino Pass, and is in the range of 
the strong, prevailing wind, which appears to be deflected back into the valley when it strikes 
the opposite mountains. 
This body of sand is many miles north of the direct line between the Pass and the Gila, and 
cannot interfere with a railroad. Sand has accumulated at several points between the base and the 
summit of the Bernardino Pass. It, however, does not remain in the open spaces, but is confined 
to the projecting spurs of the granite of San Gorgono. In these places it is always thrown to 
their leeward sides ; and scarcely any is to be found on the side where the wind acts with its full 
force. 
All the principal accumulations of sand on the desert, that are in the vicinity of the travelled 
route, have thus been considered in succession. It is evident that the sand forms but a small 
part of the surface of the Desert, and that it does not form a deep, wide-spread, and continuous 
layer ; but that it exists in isolated patches and drifts, bearing but a small ratio in their surface 
to the areas from which they have been swept. The sand-drifts are so limited in their area, 
and are separated by such wide intervals, that the transit from the Colorado to San Bernardino 
may be made without crossing one of them. A railroad track can also be laid down between 
these two places without coming in contact with a single sand-hill. 
SPRINGS, WELLS AND STREAMS OF THE DESERT.—ARTESIAN WELLS. 
On that portion of the Desert which is usually traversed by travellers and the emigrants to 
California, by the way of the valley of the Gila, and from Sonora, the main dependence for water 
is upon New River and its sloughs, and the two ponds—the Big and Little lagoons—which are, 
in fact, but portions of New River at times of high water. The wells of the Desert are on a side 
road to the northward of New River, and are not relied on by emigrants and travellers accom¬ 
panied by many animals, or by droves of cattle. New River and its lagoons cannot be relied 
upon as an unfailing source of water; it depends upon the Colorado being filled during the 
