BRICK Y^BDS 



237 



being lifted off entire or in sections. The surface of the molded 

 piece is then trimmed and smoothed, and it is put in the drying 

 room until sufficiently dry to burn. Burning is done in down- 

 draft kilns, and takes seven to nine days. The kiln has to be 

 fired very cautiously at first to prevent the ware from cracking ; 

 and the heat within it is regulated by means of dampers on the 

 roof and sides. 



Large lumps of clay are placed just inside the doors of the 

 kiln to serve as testers. When the burning is nearly done, one 

 of these is withdrawn from time to time and allowed to cool, and 

 from its appearance is determined whether the contents of the 

 kiln are burnt enough ; the kiln must be cooled very slowly in 

 order to prevent the ware from cracking ; when cool, the terra 

 cotta is taken out and is ready for market. 



The following are analyses of ]^ew York clays used for making 

 terra cotta : 





Afred 

 Center. 



Glens Falls 

 blue. 



Glens Falls 

 red. 



Elm Point. 



Silica 



53.20 



23.25 



10.90 



1.01 



.62 



2.69 



.41 



.91 



6.39 



.52 



48.35 



11.38 



4.02 



15.38 



3.17 



6.05 



57.46 

 21.15 

 5.52 

 3.65 

 1.50 

 4.72 



62.06 



Alumina 



18.09 



Iron peroxide . . . = 



Lime 



5.40 

 1.05 



Magnesia 



Trace. 



Alkalies 



6.11 



Sulphuric acid . 



Titanic acid 



Water (comb) 



Manganese oxide 









Total 



99.90 



88.30 



94.00 



92.71 



Roofing-tile 



Alfred Centre is the only locality in New York at which roof- 

 ing-tile are being manufactured. The Celadon Terra-Cotta Co. 

 has been in operation for several years, and another factory has 

 recently commenced operations. The material used is a mixture 

 of local bluish gray clay and a Devonian shale. These two are 

 thoroughly ground in dry pans, from which they are carried to 



