FIRE CLAYS. 155 



worthy of notice, and show it to possess character 

 closely resembling those of many glass pot clays. 

 The composition of this clay is as follows : 



Analysis of Fire Clay, Tuscaloosa Co. (No. 118). 



Silica 58.13 



Alumina 24.G8 



Ferric oxide 3.85 



Lime 15 



Magnesia 32 



Alkalies 1.78 



Ignition 11.78 



Total fluxes, 



The rational composition is: 



Clay substance 60.85 



Quartz 23.35 



Feldspar 15.80 



100.00 



Glass pot clays vary in chemical composition, and 

 it is really the physical behavior of the material 

 which it is of importance to know. At the same time 

 the analyses of several other glass pot clays are given 

 below for comparison. 



Analysis of Glass Pot Clays ' 



No. 1. 



Silica 64.89 



Alumina , 24.08 



Ferric oxide 29 



Lime 41 



Magnesia 19 



Potash 87 



Soda 16 



Ignition 9.29 



