44 
TRANSACTIONS OF THE TEXAS ACADEMY OF SCIENCE. 
Wasiiita Limestone.— These are the most extensive of the Grand 
Prairie soils, in its eastern portion, and occupy nearly its whole area 
north of the Brazos river. They comprise the rich prairie lands of the 
western parts of Hill, Johnson, Tarrant and other counties. 
The character of the topography is such as to favor the accumulation 
of deep soils, except where cut by creeks, and is sufficiently rolling to 
afford good drainage. 
The soils are dark brown marls, and even in the areas where the topog¬ 
raphy is most rugged form good pasture lands. 
Their exceptional ferlility does not appear to be caused by the percent¬ 
ages of potash and phosphoric acid that they contain, so much as by their 
fine physical condition. 
The brownish black marl of the Washita is well illustrated by the anal¬ 
ysis No. 32 from Johnson county. 
32* 
Insoluble matter. 60.354 
Soluble silica. 5.563 
Potash.365 
Soda. Trace. 
Lime . 9.780 
Magnesia.70S 
Manganese .030 
Iron. 5.346 
Alumina. 5.746 
Phosphoric acid. 178 
Sulphuric acid.047 
Carbonic acid. 6.594 
Water and organic matter. 5.255 
99.966 
♦Cotton Production, Tenth Census, p. 36. 
Fredericksburg. —The soils of this division in the eastern portion are 
usually thin, as by reason of the sharpness of the topography the mate¬ 
rials are carried away almost as fast as they are disintegrated, and conse¬ 
quently there is little chance for the accumulation of soil. Sometimes, 
however, these rocks occupy the summits of divides and give rise to dark 
brown or rich black residual soils. 
Ordinarily the rocky surface is covered by a stunted growth of timber 
or by harsh grasses. 
Residual soils from the Fredericksburg division are represented by 
analysis 33, from Travis county, and 34 and 35, soil and subsoil from 
Williamson county. 
