IKON 



955 



of blast and rich burden of materials that a cast of several tons was obtained within, 

 14 hours after applying blast. The first week's blowing produced 200 tons, at which 

 r ite it continued for two or three weeks, when it rapidly diminished, falling so low as 

 1 9 tons for one week's make. From this deplorable state it was made to produce 26 

 tons, and, after considerable delay, 100 tons ; but with a large increase in the yield of 

 materials over that at the other furnaces. When a furnace is first blown in it should 

 be made to produce grey iron ; but the tendency of forcing is to produce a white iron 

 with a dark scouring cinder. 



The quantity of air thrown into a blast-furnace in full work is enormous, exceeding 

 in weight the totals of all the solid materials used in smelting. A furnace working 

 on foundry iron of a capacity of 275 yards receives 5.390 cubic feet of air per 

 minute, which amounts weekly to 1,695 tons ; when working on white iron a larger 

 volume of blast is employed, averaging 7,370 cubic feet per minute, or 2,318 tons per 

 week. 



The disorders to which blast-furnaces are liable have a tendency to produce white 

 cast iron. The colour of the slag or scoriae is the surest test of these derangements, 

 as it indicates the quality of the products. If the furnace is yielding an iron proper 

 for casting into moulds, the slag has an uniform vitrification and is slightly translucid. 

 When the dose of or?e is increased, the slag becomes opaque, dull, and of a greenish 

 yellow tint, with blue enamelled zones. Lastly, when the furnace is producing white 

 metal, the slags are more or less black and glossy. The scorise from a coke are much 

 more loaded with lime than those from a charcoal blast-furnace. This excess of lime 

 appears adapted to absorb and carry oS'the sulphur which would otherwise injure the 

 quality of the iron. From numerous analyses Dr. Noad made of blast-furnace cinders', 

 we select the following as illustrating their general composition under different conditions 

 of the furnace : 



Analyses of Blast Furnace Cinders. 



The following Table exhibits the ' yields ' of materials per ton on the iron made 

 in various works. During the month ending July 25, 1857, there were consumed 

 in four furnaces at Ebbw Vale 1,354 tons 14 cwts. of coke ; 1,792 tons of coal ; 2,440 

 tons 19 cwts. of calcined mine ; ],818 tons of 10 cwts. red ore; 1,347 tons 6 cwts. of 

 calcined cinders ; and 1,226 tons 7 cwts. of burnt lime. The quantity of pig-iron made 

 was 2,305 tons 7 cwts. : 



Yields of Materials per Ton of Iron. 



