50 
TRANSACTIONS OF THE TEXAS ACADEMY OF SCIENCE 
In the areas occupied by the newer limestones black loamy and marly 
soils are found. 
TRANS-PECOS REGION. 
In this area the principal soils are those of the ancient lake basins or 
flats which separate and surround the various peaks and mountain ranges. 
The soils are usually red loams, with variable proportions of sand and 
clay, and sometimes with sufficient lime in them to take on a marly char¬ 
acter. 
The materials of which they are composed have been derived from the 
disintegration of the rocks of the mountains among which they lie. 
These consist of sandstones, limestones, clays, granitic and various erup¬ 
tive rocks which are often rich in potash. The analyses of the soils of 
this area clearly show the effect of such a mingling of materials, and the 
percentages of those important plant foods, potash and phosphoric acid, 
are much above the average. Their fertility is proved by the fine grasses 
they produce, and with a proper water supply these flats could be made 
the granary of the State. 
While the rainfall is not sufficient to render farming as ordinarily fol¬ 
lowed a possibility in this region, it is sufficient to furnish a water supply 
for a large amount of irrigation, and numerous localities exist within the 
mountains where, at comparatively small expense, dams and storage res¬ 
ervoirs can be constructed which in the aggregate will furnish, in ordinary 
seasons, enough water for irrigating thousands of acres of these fertile 
flats. It is only a question of time until they will be so utilized, and add 
their proportion to the agricultural productions of the State. 
Two analyses of the soils of the Trans-Pecos basin region are given. 
One of them (No. 44) of the red loam proper, the other, No. 45, of the 
more calcareous soil from south of Sierra Blanca. 
44* 
45* 
Insoluble matter... 
78.63 
66.55 
Soluble silica. . 
Potash . 
.44 
.52 
.17 
.47 
.46 
.29 
Lime. 
.57 
13.65 
Magnesia. 
.96 
7.44 
2.88 
Alumina. 
2.22 
1.45 
Phosphoric acid. 
.34 
.21 
Sulphuric acid. 
.38 
Trace 
Carbonic acid. 
Trace 
9.52 
Water and organic. 
8.33 
3.10 
99.33 
99.25 
* Bulletin No. 2, Geol. Sur. Texas, p. 11, 
