390 SECTION MECHANICS. 



is not found practicable to work furnaces, of the ordinary form, much 

 exceeding fifty-two feet in height. In the self-coking furnace, how- 

 ever, as it is termed, of Mr. Ferric, the barrier thus imposed to 

 increased economy appears to be got over successfully, and in a 

 somewhat remarkable way. Mr. Feme's furnace is eighty-three feet 

 high, with a closed top, the charging being effected by a bell and 

 cone ; and for a height of thirty feet, near the top, the shaft is divided 

 by cross walls into four sections. These cross walls and the cor- 

 responding portions of the side walls are built hollow, with flues in 

 their thickness, in which a portion of the gas is burned, so as to assist 

 the ascending current, in the furnace, in coking the coal and heating 

 up the charge. The amount of raw coal that this furnace burns is 

 thirty-four hundredweight per ton of iron made, against nearly 

 fifty-three hundredweight in ordinary furnaces, fifty-two feet high, 

 and working under the same conditions : a difference of about 

 nineteen hundredweight. Mr. Bell, who has studied the working of 

 the Ferrie furnace, attributes this saving, half to its increased height, 

 which is rendered practicable by the additional support given to the 

 charge by its friction against the cross walls, and half to the effect of 

 the heat communicated, through the walls, by the burning of a part of 

 the gases in their flues.* 



The older, and still the more common, method of heating the air for 

 blast furnaces is by passing it through a series of cast iron pipes, 

 heated to redness, by the waste furnace gases or otherwise, in suitable 

 hot blast stoves. The greatest temperature of blast that can be 

 maintained, in this way, without causing the rapid destruction of the 

 pipes, hardly exceeds, however, 550 C. to 600 C. ; and where higher 

 heats are desired, recourse must be had to the system of regenerative 

 fire-brick stoves, first introduced by Dr. Siemens and Mr. Cowper.t 



A model of one of Mr. Cowper's stoves is on the table. In principle it 

 s very simple. Each stove consists of a large cylinder of boiler plate, 

 lined with fire-brick work, and filled with loose fire bricks, stacked 

 together so as to form a series of vertical slightly zigzagged flues, and 

 to expose the greatest possible extent of surface. To heat the stove, 



* Journal of the Iron and Steel Institute, March soth, and August 29th, 1871. 

 t E. A. Cowper, Proceedings of the Institution of Civil Engineers, vol. xxx. p. 309. 

 C. Cochrane, Proceedings of the Institution of Mechanical Engineers, 1870, p. 62. 



