E. T. DUMBLE-THE SOILS OF TEXAS. 43 
Phosphoric acid.093 
Sulphuric acid.045 
Water and organic. 2.785 
99.886 
*Cotton Production, Tenth Census, p. 29. 
Difference of climatic conditions are well shown in the Black Prairie 
belt. The black waxy character of the soils extends to San Antonio, but 
in the more western portions of the State the soils from these beds do not 
show that waxiness so clearly nor are they always so black. The belt is 
quite narrow along the Southern Pacific railroad west of San Antonio 
until the Rio Grande is reached, when it again broadens out to a consid¬ 
erable width. A large amount of glauconitic material is found, and the 
soils, when irrigated, will doubtless sustain their reputation for fertility, 
which they so well deserve in the more humid portion of the State. 
SOILS OF THE GRAND PRAIRIE. 
The soils of the Grand Prairie are often shallow and rocky, but wherever 
they are perfectly formed and of sufficient depth and extent for cultiva¬ 
tion they are very fertile. 
Vola and Arietina.— Residual soils from the upper members of this 
belt are not extensive, since they are usually mingled with the sand from 
the Lower Cross Timbers in the region where they have the most avail¬ 
able exposure. This commingling, however, adds to their value, making 
them lighter by the mixture of sand with their rich calcareous clays. 
They are unsurpassed for the production of grain, fruits, berries and 
garden products. The width of the belt varies from a few hundred yards 
to a mile, and has the Lower Cross Timbers for its eastern border. 
Analysis 31 of a soil from Williamson county shows the richness of 
the residual soil from Arietina cla}'. It is high both in potash and phos¬ 
phoric acid. 
31* 
Insoluble matter. 63.80 
Soluble silica... 17 
Potash.51 
Soda ..50 
Lime... 2.08 
Magnesia.58 
Iron. 4.66 
Alumina. 8.99 
Phosphoric acid...53 
Sulphuric acid .. 15 
Carbonic acid ... 1.57 
Water... 3.89 
Organic and volatile . 12.81 
* Third Annual Report Q-eologipal Survey of Texas, p. 379, 
100,24 
