IRON 



1003 



The blast machines are fans, the best form of which is shown in fig. 1263 (Over- 

 an). The wings of this fan are encased in a separate box ; a wheel is thus formed, 



1262 



which rotates in the outer box ; the figure shows a horizontal section through the axis. 

 The wings are thus connected, and form a closed wheel, in which the air is whirled 

 round, and thrown out at the 

 periphery. The 

 which revolves 



1263 



inner case, 

 with the 



wings, is fitted as closely as 

 possible to the outer case, at 

 the centre near a, a, a, a. The 

 speed of the wings is some- 

 times as much as 1,800 re- 

 volutions per minute. The 

 motion of the axis is produced 

 by means of a leather or India- 

 rubber belt and a pulley, 

 This variety of fan is used 

 at the puddling furnaces at 

 Ebbw Vale, where the fuel is 

 small coal. 



Fig. 1264 is a horizontal section of the double anthracite puddling furnace. The 

 grate measures 3 feet by 5. The width of the furnace externally is from 5g to 6 feet. 

 The hearth is usually 6 feet in length. It has two work-doors, one directly opposite 

 the other. Two sets of workmen are required, therefore, at the same time ; double 

 the quantity of metal is charged, and the yield is twice that of a single furnace ; the 

 economy is in the room, fuel, and labour ; one good puddler only being required to 

 manage the operation. Double puddling furnaces are also used in several works in 

 England ; but as Mr. Truran observes, the economical advantages attending them in 



1264 



point of fuel are lost if the puddlers do not work well to time : they must bring their 

 heats to the respective stages simultaneously, for if one is kept waiting for a short 

 period by the other, the loss of iron more than balances the reduced consumption of 

 coal. The difficulty of obtaining men who will work well in concert has operated 

 against the use of the double furnace, which would otherwise certainly supersede the 



