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They enter into the construction of all furnaces for iron, or steel, or pottery, or glass, or the various other products of high temperatures, and are an absolute necessity in the proper development of such manufactures. Of such substances fire clay is doubtless the most important The essentials for a good fire clay are not so much the proportions of silica and alumina, although the larger the percentage of silica the greater its refractory power seems to be, but its freedom from materials such as lime, soda, potash, magnesia, or oxide of iron, which could unite with the silica and form a glass, and thus cause fusion.

FIRE CLAYS.

Of our Texas fire clays only two or three have had any decided or extensive trial. These are from the beds found in Henderson, Limestone, and Fayette counties. The first two are found in connection with the Timber Belt Beds, the third in the Fayette Beds. In use the brick made at Athens from the Henderson County clay have proved to be of excellent quality. They have stood the severe test of the iron furnace at Rusk and of some of the lime kilns, and are highly recommended for their good qualities. The brick from the beds of Limestone County are also of good quality, and proper care in their manufacture will make them fully equal to any. The Fayette Clays which have come under my notice, which are classed as fire clays, seem to be somewhat high in fluxing constituents, but more careful selection of the clays may entirely obviate this difficulty.

The fire clays are found usually in connection with the lignite beds, and in the Central Coal Field directly underlying the coal seams. They are therefore found scattered over a wide area of the State, but only a few of them have been examined by the Survey. These are nearly all from Eastern Texas, and were collected during the past field season. While they have not yet been fully studied, numerous analyses have been made, and it is found that many of them are too "fat," or contain too much alumina for use in the state in which they are dug, but require a large mixture of sand to correct the excessive shrinkage that would otherwise take place in drying them, amounting in some specimens to one-fourth of their original bulk. Others, however, are of excellent quality, and careful selection of localities for mining will yield very favorable results, and clays be secured suitable for brick for furnaces, kilns, ovens, fire boxes, retorts, saggers, and the many other similar articles.