40 
TRANSACTIONS OF THE TEXAS ACADEMY OF SCIENCE. 
As a whole the soils of the Black Prairie may be classed as marls, being 
usually more or less calcareous clays. The exceptions to this are the soi’s 
of the Lower Cross Timbers which mark the western border of this plain 
from Red River to the Brazos near Waco. 
The most easterly portion of this belt, which is occupied by the Navarro 
or Glauconitic beds, contains a considerable amount of greensand marl, 
and is somewhat lighter soil than that of the black waxy proper to the 
north or west of it. 
Two examples are given of the soils produced by the glauconitic beds. 
The first of these, No. 23, is taken from near Corsicana, and is the dark 
prairie soil. No. 24 is a soil and its subsoil from Delta county. 
23* 
24+ 
T ri soluble matter. 
87.557 
79.68 
58.22 
Soluble silica. 
5.183 
.08 
2.28 
Potash . 
.117 
.18 
.95 
Soda. 
.070 
.61 
1.35 
T.imfi. 
.320 
.99 
10.90 
Magnesia. 
.191 
Trace. 
.24 
Manfanesfi. 
.083 
Iron . 
1.G38 
2.85 
3.51 
Alumina. 
2.394 
2.88 
7.70 
Phosphoric acid. 
.229 
.02 
.12 
Sulphuric acid. 
.110 
.17 
.14 
('arhonic acid . 
7.77 
W ater. 
[- 2.623 
5.59 
5.14 
Organic and volatile.. 
6.92 
3.72 
100.515 
99.25 
100.12 
* Cotton Production, Tenth Census, p. 27. 
t Records Geol. Sur. Tex. Analyst, P. S. Tilson. 
The black waxy soils overlie three distinct beds of rock material: The 
Ponderosa marl, Austin chalk, and Eagle Ford clay. 
Ponderosa Marl.— The soils of the Ponderosa marls are usually of a 
dense black color, running high in percentages of lime and clay. While 
analyses do not show very high percentages of phosphoric acid in these 
soils, it is present in sufficient quantity to render the soil highly fertile 
and enduring. Should they begin to deteriorate, it will only be necessary 
to resort to deep plowing and to mix the subsoil with the soil in order to 
restore fertility. These soils have high water absorptive and retentive 
power, and except that when wet they are very hard to work, they are 
all that could be desired. Their amelioration may be possible by the 
gradual addition of ash or organic matter from burning the stalks of 
cotton or corn or other coarse crops, or by plowing them under, prefer¬ 
ably the former. 
The soils of this portion of the belt cover an area of 10,000 square 
miles, with an exceedingly small amount of waste or unproductive lands. 
