44

In the western portion of Arkansas the calcareous rocks of this group occur mostly in massive beds of great purity. Their color varies from light gray to blue and brown. They are usually highly crystalline, and sometimes contain irregular masses of talc-spar. Occasionally they are homogeneous in texture, breaking with a smooth conchoidal fracture, and of a bright fawn color.

In the Choctaw Territory, a hundred miles southeast of Fort Smith, the limestone is hard, compact, and of a light blue or drab color. It is there largely intermixed with chert, and as far as exposed contains no layers of sandstone.

On the Upper San Saba River it is thin bedded, of a dull gray color, and more or less granular. The sandstone is hard, coarse grained, and highly ferruginous, sometimes passing into silicious iron ore, and in color varies from deep brown to red and black. In places it is highly metamorphosed. In the Organ Mountains the limestone is hard, highly crystalline, and occurs in layers of variable thickness, being in some places massive and in others thinly laminated. Its prevailing color is blue, from which it passes into various shades of gray, brown, and black. The sandstone is both coarse and fine grained, and usually of a light yellow color. These rocks are here traversed by tortuous veins of quartz, talc and fluor spar, and often exhibit a highly metamorphosed appearance.

In the Fra Cristoval Mountain these rocks do not differ in general character from what is observed in the Organ Mountains.

Like that of the preceding group, the country occupied by the Lower Carboniferous rocks exhibits strong evidence of subterraneous disturbance, as well as of subsequent denudation, and is characterized by a rough and broken surface, lofty mountains, rugged precipices, and great variety and beauty of scenery.' Wherever favorably situated with regard to climate, as in Western Arkansas, it is well supplied by innumerable springs with the best of water, covered with highly productive soil, and it well affords every inducement for the agriculturist.

These rocks furnish excellent building materials. The limestone and sandstone are both hard and durable, and are, therefore, well adapted for