248 
GEOLOGY. 
3. The lower level, or terrace, bordering the Colorado, and extending far inland, is thickly 
wooded near the Mezquite Well with mezquite, and near the Colorado with willows and cotton® 
woods. These plants show the presence of water at no great depth below the surface. 
4. The deep clay is very retentive of moisture, and evaporation from its surface is slow. 
5. Water being found in several distant places, at apparently the same level, and below the 
level of the Colorado, indicates that the supply is derived, partly at least, from that stream, by 
infiltration. 
In view of these facts, and the experience of travellers, in relation to the wells, I do not 
hesitate to assert that, when judiciously constructed, ordinary wells can be relied upon for a 
constant and abundant supply of water. 
There are many other points, intermediate to the wells, where water can be obtained by dig¬ 
ging. Indeed, it will probably be found at almost any part of the lower terrace upon which 
the mezquite grows so abundantly. The natural springs of the northern part of the Desert may 
be regarded as unfailing, and they can be made to furnish a supply of water sufficient for all 
railroad purposes. 
Artesian wells .—In addition to the water that can be obtained from common wells in the clay, 
there is every reason to believe that deep Artesian borings would be entirely successful. The 
clay formation rests upon stratified Tertiary sandstones and shales which are more or less tilted 
and disturbed by intrusive rocks. The edges of these strata appear at the surface at Carrizo 
Creek and along the base of the Peninsula Sierra. Although there is comparatively very little 
water supplied from the inland slope of these mountains, yet, in the aggregate amount, it is 
probably sufficient to keep the strata under the clay charged with water. The strata may also 
receive a supply from the Colorado. The clay formation acts as a retentive superstratum ; by 
perforating it, and reaching the underlying strata, it is probable that a copious supply of 
water would be obtained ; in some parts of the Desert, it would overflow the surface. Such 
wells would be of great value in that region for irrigation. 
In the event of the location of the railroad upon the upper terrace, or gravelly plateau to the 
north of the Sand-Hills, it may be desirable to obtain water there. It can be most conveniently 
done by boring ; and the depth to which the perforation must extend will necessarily be much 
greater than if commenced on the lower plain or first terrace. The probabilities are that water 
would be found ; but, in that vicinity, it cannot be expected to rise to the surface. 
If the railroad is constructed on this upper plain, it will be north of the boundary line, and 
avoid the long detour to the southward along the trail, which is in Mexican territory. A 
straight line from the Gila to the Bernardino Pass crosses this upper plain, and nearly intersects 
the Soda Springs and the Salt Pond. The fact that water rises in springs in the lower and 
central parts of the Desert is important, and gives additional reason to believe that Artesian 
borings would be attended with perfect success. 
AGRICULTURAL CAPABILITIES OF THE SOIL.—CLIMATE. 
The upper or gravelly plains of the Desert, especially those in the vicinity of the mouth of 
the Gila, are too arid and wanting in soil to be ever used for agriculture. But this is not the 
case with a large part of the Desert—that part formed of the alluvial and lacustrine clay. The 
whole of this clay surface may be considered as capable of supporting a luxuriant growth of 
vegetation, provided it is supplied with water by irrigation. It is undoubtedly of nearly the 
