On the Principles of Iron and Steel, 163 
but in many inftances they will alfo apply to thofe of other 
countries, where the charcoal of wood is ufed for fuel. 
Since crude iron exifts of fuch a variety of quantities, 
owing to the various proportions of mixture united with it; 
and fince it is almoft univerfally ufed to produce bar or mal-~ 
leable iron ; it is natural to infer, that there muft exift one 
particular variety of it, which could be appropriated to the 
manufaéture in preference to any other. Theory fays that 
that crude iron, carbo-oxygenated, which contains the 
alterative principles in equal portions, requires only to be 
expofed in a fluid ftate to the action of fire, either in a wind 
furnace or {mall blaft. By this expofure the carbon becomes 
volatilized, and carries off the oxygen along with it*. 
Praétice has however confined the operation chiefly to the 
forge pig (oxygenated crude iron). This variety of iron 
becomes fooner malleable, but is likewife fufceptible of 
early oxydation, and confequently liable to. become cold 
fhort. Neither can it unite to bar iron thofe. properties 
from whence are derived great firength and duétility. 
When carbonated crude iron is ufed, the wafte then is apt 
to be exceffive: the metal retains for too long a period its 
fufible principle, which muft neceffarily expofe the mafs to 
a longer continued aétion of the flame, whereby oxydation 
on the metal ina fluid ftate takes place, and a confiderable 
portion of it is deftroyed before the iron exhibit figns of in- 
fufibility. Malleable iron made from this ftate of the metal 
has a great tendency to be red fhort, and lofes alfo confider- 
ably of its weight under the forge hammer. 
It has at all times been afferted, that crude iron contains 
a confiderable proportion of its parts, by weight, inimical to 
malleability ; and that, in the operation of refining, it then 
* A definition more confonant to chemical language would be to fay, 
that the oxygen unites tothe carbon and forms carbonic ecid, which 
is expellable even in a moderate heat. The efcape of the laft portion 
of the acid is indicated by the difappearance of fufion, and the cgalefcence 
of the clotted iron, 
M2 parts 
