526 
IRON. 
into the hottest part of the furnace, where it be- 
comes fused, and the melted metal falling to the bot- 
tom, is let out by a trap-hole into furrows made in a 
bed of sand : the large mass which sets in the main 
furrow is called a sow, and the lesser ones pigs, of 
iron. Chimney backs, stoves, garden rollers, &c., 
are formed of this rough metal, taken out of the re- 
ceiver with ladles, and cast into moulds made of 
fine sand. The best raw iron, though all possible 
care may be taken to free the ore from the different 
substances with which it is mixed by the usual pro- 
cess of smelting, is never malleable. To effect this, 
the impure cast iron is melted a second time in an- 
other furnace intermixed with charcoal. The iron, 
which is then called a loop , is conveyed under a 
large hammer raised by the motion of a water-wheel, 
and there beat into a thick square form. This 
operation several times repeated, heating the metal 
each time till it is almost ready to melt, at length 
makes it completely malleable, so that it may readily 
be formed into bars for sale. Cast iron has of late 
been brought into the malleable state, by passing it 
through rollers instead of forging it. 
The tenacity, ductility, and malleability of iron 
is very great, and, according to Magellan, it exceeds 
every other metal in elasticity and hardness when 
properly tempered. An iron wire a tenth of an inch 
in diameter will support 450 pounds weight. It 
extends with some difficulty under the hammer, but 
it may be drawn into wire as fine as a hair. 
