446 CLAYS AND CLAY INDUSTRY. 



Chemical analysis of a No. i sandy fire clay. McHose Bros. 



Raw. Burned. 



Silica ( Si0 2 ) , 69.78 74.66 



Alumina (A1 2 3 ), 19.86 21.24 



Ferric oxide (Fe 2 3 ), 0.62 0.66 



Titanium oxide (Ti0 2 ) , 1.96 2.09 



Lime (CaO), Magnesia (MgO), 



Alkalies (Na-O, K.O) by dim, 1.24 1.32 



Water (H 2 0), 6.54 



99-97 



This clay is not highly refractory, and in fact is not as refrac- 

 tory as some of the No. 2 fire clay dug near Woodbridge, al- 

 though known commercially as a No. 1 sandy fire clay. It has 

 been used in the manufacture of bath tubs and stove linings. 



A sample of No. I buff clay from the same locality (Lab. No. 

 401) gave the following results on testing: 



The material was a flaky, moderately-plastic clay, which worked 

 up with 32 per cent, of water to a mass whose air shrinkage was 

 5 per cent., and the briquettes from which had an average tensile 

 strength of 65 pounds per square inch. The behavior in burning 

 was as follows : 



Burning test of a No. 1 buff clay, McHose Bros. 



Cone. 5 8 15 



Fire shrinkage, 5% 6.6% 10.3 % 



Absorption, 11.68% H-34% 2.33% 



Color, light yellow buff 



The clay was steel-hard at cone 5, but at cone 27 was not more 

 than incipiently fused. From this it is evidently of good refrac- 

 toriness. 



Sand Hills. — South of Sand Hills there is another group of 

 pits, with smaller ones between Sand Hills and Valentine. At 

 Sand Hills the excavations are far deeper and more extensive 

 than those north of Florida Grove, just mentioned. Here it is the 

 Woodbridge fire-clay bed that is opened up. The beds corre- 

 sponding to the top- and bottom-sandy of the Woodbridge district 

 are not clearly identifiable. The deepest sections exposed are in 



