ON FURNA CES. 399 



The Newport furnace of Mr. Jeremiah Head* may be taken as an 

 example of those furnaces in which blast, heated by the waste flame, 

 is introduced under the fire-grate. In this, the blast pressure is obtained 

 by a steam jet, and the resulting damp air is heated to about 290 C. 

 by passing it through a cast iron heating stove, round which the waste 

 flame is led on its way to the chimney. The hot blast is conducted 

 partly under the fire-grate, and partly to a row of holes in the furnace 

 roof, immediately over the fire, through which a supply of air is thus 

 introduced, sufficient to complete the combustion of the gases rising 

 from the fire. Mr. Head states that in a hand puddling furnace of this 

 construction, working four-hundredweight charges, the temperature 

 at which the burned gases finally pass to the chimney is reduced 

 from 1112 C. (the average temperature found in the chimney of a 

 similar furnace, in which the air was not heated) to 860 C. ; the heat at 

 the same time at the fire bridge being estimated at 1370 C. The 

 consumption of coal is reduced from twenty-four and a half hundred- 

 weight, per ton of puddled bar produced, to sixteen and a half hundred- 

 weight, and the yield is stated to be also from one to three per cent, 

 greater than in the ordinary furnace. 



In Price's retort furnace the fire is supplied with air forced in by a 

 fan, and heated by the waste heat to between 200 and 260 C., and 

 the coal used is also heated, before it is pushed forward on to the grate,. 

 by charging it through a high vertical retort, round which the spent 

 flame passes to the chimney. The saving in fuel effected, in fur- 

 naces for puddling and heating iron, by thus making use of the waste 

 heat, is stated to amount to between thirty and forty-five per cent. 



An American arrangement, known as Frisbie's feeder, that has been 

 recently introduced into this country, avoids in a different way the 

 cooling of the surface of the fire each time that fresh coal is put on ; 

 and the burst of smoke, after firing, from the evolution for a short 

 time, from the suddenly heated fuel, of hydrocarbon gases and vapours 

 that pass away only partly burned ; as well as the necessity for fre- 

 quently opening the fire door. In this mode of firing, each charge of 

 coal is filled into a moveable charging box, and pushed up, from below, 



* Journal of the Iron and Steel Institute, 1872, pp. 220 et seq. 



