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hard under water. Portland cements are of similar character, but are made by artificially mixing the limestone and clays in the proper proportion.

Materials for both characters of cement exist in abundance within the State. The limestones of certain beds of the Cretaceous are argillaceous enough to make cement when properly calcined and ground, and the same properties are claimed for some of those found in the Tertiary, but our tests have so far failed to bear out the claim. Some of the limestones belonging to the Clear Fork Beds of the Permian might answer if the percentage of magnesia was not too great.

The materials for Portland cement are, however, more abundant, and the product of so much better quality as to render the natural cement a matter of comparatively small importance. The Austin Chalk is rather widespread in its distribution and adjacent to clays of almost any required grade.

The entire practicability of the manufacture of Portland cement has been shown by the two factories which have undertaken it, one at San Antonio, the other at Austin. The former supplied much of the cement used in the erection of the present Capitol building, and as the reports of it by Gen. Gilmore show, it was of very excellent quality.

The works at Austin are now under way, and it is proposed to increase their capacity.

PLASTER PARIS.

Plaster Paris is produced from gypsum by driving out the percentage of water which is chemically combined with it. Its manufacture on any desired scale is entirely practicable in the Permian region of Texas, where many beds of gypsum of great purity occur.

SANDS FOR MORTAR, ETC.

Sand for mortar, plaster, etc., is found in many places. The Cretaceous is perhaps the area in which it is scarcest, and it can be brought in from either side. The locations will be more fully discussed in the descriptions of counties.

METALS AND ORES.

IRON.

Probably the most important of our ore deposits are those of iron, which in various forms are found in many parts of the State.