IRON 



and the outlet main, 3 feet in diameter, is lined with fire-brick 9 inches thick. Fig. 

 1235 shows the general arrangement of those stoves as applied to a blast-furnace at 

 Consett in Durham. They are four in number, each being 22 feet in diameter, and 

 25 feet high, and containing 250 tons of brick, arranged so as to give 9,000 feet of 

 heating surface. They are worked in pairs, the current being changed every two hours. 

 The furnace makes from 400 to 600 tons of pig-iron per week, with an average con- 

 sumption of coke of 19 to 19| cwts. per ton ; the ore yields about 45i per cent. The 

 effective blast-temperature is from 1,100 to 1,300 Fahr. 



Mr. Truran, in his work on the iron manufacture of Great Britain, gives it as 

 his opinion that the effects of hot blast have been greatly exaggerated, and that it 

 is to improvements in the preparation of fuel and ore in the furnaces, in blowing en- 

 gines, and in the smelting process, far more than to the heating of the blast, tli.it AVO 

 must refer the great reduction in the yields of coal in recent times ; he thinks that 

 the comparatively large produce which has been obtained from the Scotch furnaces is 

 to be referred to the general use of carbonaceous ore, which melts at a low tempera- 

 ture ; and which, from its comparative freedom from earthy matters, requires but a 

 minimum dose of limestone for fluxing. Against this opinion of an English writer on 

 iron smelting, we may place that recorded by an American metallurgist, Mr. Overman, 

 who has written a large and in many respects a valuable treatise on the manufacture 

 of iron, as conducted in America. 'The economical advantages arising from the 

 application of hot blast, casting aside those cases in which cold blast will not work at 

 all, are immense. The amount of fuel saved in anthracite and coke furnaces varies 

 from 30 to 60 per cent. In addition to this, hot-blast enables us to obtain nearly 

 twice the quantity of iron within a given time that we should realise by cold blast. 

 These advantages are far more striking with respect to anthracite coal than in relation 

 to coke or to bituminous coal. By using hard charcoal, we can save 20 per cent, of 

 fuel, and augment the product 50 per cent. From soft charcoal we shall derive but 

 little benefit, at least where it is necessary to take the quality of the iron into con- 

 sideration.' 



The following Tables, embodying the general results of an extended series of experi- 



