11 



and thread guides; smoking pipes ; umbrella stands ; pedestals; filter tubes; 

 castor \\beels ; i)iini]) wheels. 



Refractory wares. Crucibles ami other assaying apparatus; gas retort* ; lire 

 bricks; glass pots ; blocks for tank furnaces ; saggers; stove and furnace bricks ; 

 blocks fot lift- boxes; tuyeres; cupola bricks. 



Engineering works. Pu&dle; Portland cement; railroad ballast; water con- 

 duits ; turbine wheels. 



THE TKST1XU AND KXA.M IN ATK >\ OF CLAYS. 



Although tlu> testing of clays does not properly Fall within tin- scope 

 of a paper of this nature a>few words on the subject will probably be of 

 interest. There is a very widespread- impression that the nature and 

 uses of a clay body will be revealed by a chemical analysis alone. It 

 is true that combined with other data the results of complete chemical 

 analysis are always of value, but the fact remains that clays of widely 

 different properties will have almost identical chemical composition and 

 vice versa. This is illustrated by the analysis of two samples, one a 

 fat ball clay from Florida, and the other a rather lean fire clay from 



Kentucky. 



Chemical analyses of two clays. 



In addition to the usual chemical analysis, it is customary to exam- 



[ ine clays by methods of so-called rational analysis, in which the effort 



; is made to distinguish between the silica which is combined with 



alumina as clay substance and that which is free as quartz or sand. 



While somewhat inaccurate such analyses are of undoubted value. 



The amount of water required to be mixed with air-dried clays to bring 

 i them to just the proper consistency for molding into forms varies 

 greatly in different clays. It is evident from what has been said in an 

 earlier paragraph that the smaller the amount of water present the less 

 the danger from air shrinkage and the greater the economy of working, 

 especially when artificial heat is used in the drying process. In a 

 thorough report on the useful qualities of a clay this properly should 

 always be tested. The physical characteristics which it is necessary to 

 test in a complete examination of clay are best shown by the following 

 laboratory form : 



