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At the distance of about fourteen miles these rocks were succeeded by heavy beds of blue marly clay and hard and soft chalky limestone, which continued to be largely exhibited during the remainder of the distance to San Antonio.

Iron ore was again frequently met with to-day, and specimens of brown hematite of excellent quality were collected. The indications were such as to lead to the belief that this important metal exists here in considerable quantity.

The surface of the country for the first fourteen miles was thickly covered with loose pebbles and small boulders, derived principally from the destruction of the conglomerate. But as we approached San Antonio the soil became quite fertile and often clothed with luxuriant vegetation. Soil and sub-soil calcareo-argillaceous.

Distance, 20 miles.

While the expedition was detained several days in San Antonio, I employed my time in the examination of the geological structure of the country in that vicinity.

The Cretaceous System is here well developed, and consists for the most part of nearly horizontal strata of light gray limestone; thin bedded, fine-grained, and compact sandstone; and indurated marly clay. These beds correspond in geological position and, with the exception of the limestone, lithologically with the strata occurring between this place and Victoria, which we have already described.

The limestone, which constitutes the upper part of the Cretaceous System around San Antonio, has been extensively worn away by denudation. In some places it is very thin or entirely wanting; in others it forms gracefully rounded hills with gentle slopes; and at others again presents precipitously in bold and rugged escarpments. This last character is well exhibited near a small creek, known as the Salado, eight miles northeast of the city, where a range of gently sloping hills terminate abruptly to the southwest in a long line of bold and nearly vertical cliffs, over a hundred feet in height.

This rock varies considerably in character, and exhibits almost every degree of hardness. When first taken from the quarry it is often quite soft, white, or of a light gray color, and can hardly be distinguished from chalk; but after exposure to the atmosphere it soon hardens to form a most useful and durable building material, for which purpose it is largely employed in San Antonio. When first quarried it is easily cut with a knife, or common band saw, into convenient sized blocks, which are exposed for a few days to the weather, and are then fit for use. While in the city I was shown a number of old buildings constructed of this material; one of them a church,