CHI2JA CLAYS. 131 



cent., and 4 per cent, in burning, making a total of 

 11 per cent. 



The tensile serength of the air dried briquette was 

 quite low, being 40' pounds per square inch on the 

 average, with a maximum of 53 pounds per square 

 inch. 



Incipient fusion occurs at 2200° F., vitrification at 

 2400° P., and viscosity at 2600° F. 



The clay burns to a white body which is hard and 

 dense, the following is the analysis of the clay. 



Analysis of Ohma Clay, Pegram, Colbert Co. (No. 56, S.) 



Total Silica 64.90 



Alumina '. 25.25 



Water 8.00 



Moisture .~ .90 



Ferric oxide trace 



Lime trace 



Magnesia trace 



99.05 



F ee si' a 34.40 



Specific gravity 2.35 



The material is to be looked upon as a white-ware 

 clay of good grade, from which the sand could be re- 

 moved by washing if necessary. There are practical- 

 ly no published analysis with which this agrees very 

 closely, but a comparion is not necessary as tlie purity 

 of the matei-ial is self evident. 



FIEE CLAYS 



The term fire-clay is applied to those clays which 

 will resist a high temperature without fusing. 



Fire clays are of two kinds, flint clays and plastic 

 clays. 



The flint clays generally approach kaolinite in com- 

 position, but have no plasticity, or at the most a very 



