Mr. J. Napier on Copper Smeltinfj. 269 



round numbers as under : — 



SiUca 61 



Per- and jjrotoxide of iron . 27 



Alumina 5 



Lime 4 



Magnesia 1 



Sulphur 1 



Carbon 1 



Too 



Le Play gives the composition of a clinker as — 



Silica 52 



Peroxide of iron . . . 5'2 



Protoxide of iron . . . 22'0 



Alumina 14-2 



Lime 2*4 



Magnesia '7 



Sulphur 1'3 



Iron 1-0 



Carbon 1'2 



1000 



With coals which give but a small quantity of a white and 

 slaty ashj as some of the Newcastle varieties, a little ground slag 

 or oxide of iron put into the fire will assist the formation of a 

 proper clinker. 



The advantages of this method ofkeeping the fire are obvious. 

 The clinkers are bad conductors, which, with their thickness 

 from the lowest part to where the fire is active, and the current 

 of air passing up through them, prevents the heat from being 

 radiated into the ash-pit. Moreover the air in passing through 

 this mass of clinker gets heated, an advantage of no little im- 

 portance in large fires. 



The clinker being thus brought nearly level with the bridge, 

 and the fire reaching to the roof, it will not burn upwards, but 

 horizontally ; so that when the furnace is in operation, it may 

 be looked upon as a blast or cupola laid upon its side to prevent 

 the materials mixing with the fuel. 



It will be seen that the materials placed in the bed of the fur- 

 nace to be smelted are not only subjected to a high heat, but are 

 exposed to the action of the gas or gases given otf by the fuel; 

 and thus the nature of these gases and their power of acting upon 

 the stuff are important considerations in the operation. The 

 fpiantity of air admitted through the fire will modify materially 

 the ([uaiitity and quality of these gases, and for some operations 

 effect certain deleterious reactions in the materials to be smelted. 



