lxxiv REPORT OF THE STATE GEOLOGIST. 



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 man- 

 ufactures. 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, Lime- 

 stone, 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 Busk 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 en- 

 tirely 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 re- 

 quire a large mixture of sand to correct the excessive shrinkage that 

 would otherwise take place in drying them, amounting in some speci- 

 mens to one-fourth of their original bulk. Others, however, are of ex- 

 cellent quality, and careful selection of localities for mining will yield 

 very favorable results, and clays be secured suitable for brick for furn- 

 aces, kilns, ovens, fire boxes, retorts, saggers, and the many other simi- 

 lar articles. 



