269 
ment of pigs ; and it is necessary for this purpose that we 
should keep an assortment of pig iron from various parts of 
the kingdom, and even from India. A great deal of iron in 
Staffordshire is what is termed double worked or ball-fur- 
naced; that is, it is cut down, piled heated in a furnace 
in the forge (usually on a sand bottom) called a ball fur- 
nace, taken to the hammer, shingled, and rolled into a bar, 
which is again cut down and piled in the mill, sometimes 
only the top and bottom, and sometimes the whole pile, being 
formed of this reheated iron ; the object of this additional 
process being to give the iron sufficient tenacity and mallea- 
bility to roll without cracking, into angle and T iron, and a 
great variety of different shaped bars, used for particular 
purposes, and commonly termed fancy iron. The top and 
bottom piles of rails are always ball-furnaced. The ball- 
furnace is also used for working up scrap into bars. 
Soundness Unsoundness is perhaps not a mystery, but it is, 
nevertheless, still a desideratum to know how to make perfectly 
sound iron without a great additional expense of manufacture. 
The larger the bar, the more difficult to make it perfectly 
sound. The unsoundness consists chiefly of a thin layer, or 
of particles of protoxide of iron. All iron heated to a certain 
temperature becomes immediately coated with the blue pro- 
toxide of iron, which is an obstacle to perfect welding. The 
use, I believe, of borax in welding, is to form a flux to this 
protoxide, which being then squeezed out by the blows of the 
hammer, two surfaces of pure iron being brought into perfect 
contact, a perfect weld ensues. All the holes and inequali- 
ties of the puddler's ball, as soon as it is drawn from the 
furnace, become immediately covered with a thin film of pro- 
toxide of iron ; this is doubled in under the shingling hammer. 
Then again the puddle bars all become coated with the same 
blue film, and when heated together in the furnace, so much 
as does not run out in the furnace, or get squeezed out 
