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fountain of inestimable value to another region beneath which it lies concealed and usually unappreciated.
Wherever the surface outcrop of these sands has attained any areal extent, they are covered with a comparatively abundant scrubby forest growth, as conspicuously illustrated in the case of the Upper Cross Timbers. The sandy soils resulting from their disintegration, however, are not as rich in fertilizing ingredients as the overlying calcareous soils, but they can be greatly improved by mixtures. The soils, as indicated by their natural vegetation, are the best adapted to tree growth, and are becoming the seat of a fruit growing industry.
The lignites and occasional iron ores in the Trinity sands are worthless, and the alleged gold discoveries existing in nearly every neighborhood invariably turn out to be iron pyrites.
NO. 2. THE FREDERICKSBURG DIVISION.
In the high bluffs of Cow Creek, in the western edge of Travis county, immediately below Mr. Hensel's house, at Travis Peak postoffice, the Trinity sands can be seen gradating upwards into this division, the lowest beds of which are marked by the appearance of certain magnesian sandy marls and rocks, accompanied by the presence of certain fossils, which we have called the Caprotina Horizon No. 1. According to our classification in the general section given beyond, this is the base of the Fredericksburg division, and is principally composed of calcareous matter with apparently equal parts of fine quartz sand and magnesia, in bands or strata of alternating degrees of consolidation. Although showing a deeper and more uniform sedimentation than the Trinity sands, yet, as shown by the alternating sediments, the chalky, deepest sea, conditions of the Comanche Peak beds have not yet been reached. The alternation of harder and softer layers of arenaceous-calcareous strata prevails, and the beds become thicker and more massive as the ocean's bottom descended. Such is the beginning of the beds to which I have applied the name of the Fredericksburg division, which may be divided into three lithologic subdivisions, to-wit:
- (c) The Caprina Chalky Limestone Beds.
- (b) The Comanche Peak Chalk Beds.
- (a) The Basal or Alternating Beds.
This division is named after the town of Fredericksburg, whose vicinity was visited by Dr. Ferdinand Rœmer, now Professor at Breslau, Germany, forty-five years ago (1845-1847). This gentleman, who might be termed the pioneer of Texas geologic investigation, described many of the unique fossil remains of the rocks which we now place in this division.