<-On the Principles of tron‘and Steck. 159 
*gsore valuable will be the pig iron. A fparing proportion oF 
charcoal in the blaft furnace is productive of effects com- 
pletely contrary to thefe, 
It moft naturally occurs to enquire, to what extreme de- 
gree of combination thefe alterative principles are capable of 
with iron, and in what ftate the metal is when this exceffive 
faturation is completed. : 
If crude iron is expofed in fufion, for a length of time, to 
abiorb carbon, and at the fame time is protected from 
oxydation, it will receive this principle to fuch excefs as to 
form a true plumbago. In this ftate it either refembles ftecl, 
grained lead ore, or affumes an imperfect cubical cryftallifa- 
‘tion, wonderfully brittle, and poffeffed of a real metallic ap- 
pearance and weight: in this ftate it is powerfully attracted 
‘by the magnet. 
Specimens »f this fingular combination are extremely 
rare; feveral that | am in poffeffion of,. have regular faces 
approaching to a cubical ftruéture, with furfaces chequered 
with numerous diagonal lines interfeéting each other, and 
‘forming rhombufes : thefe are eafily difplaced with a knife, 
and exhibit them compofed of the thinneft lamine imagina- 
ble: in this ftate they are nét obedient’ to the magnet, unfely 
“a confidérable number of them are attached togethér. The 
fpecific gravity of this mixture of iron and carbon is to 
“water as 6°9694 to.1'000; a cubic foot weighs 435°58750 
“pounds avoirdupoife. 
‘Jn manufacturing crude iron, the higheA poffible pitch to 
“which it can be united with oxygen is productive of a coarfe 
“metallic fubftance, whofe fra€ture is dark and porous, arid 
whofe furface on cooling becomes covered with a deép 
“earthy oxyd; incapable'of being fufed but by bisaricineee 
‘a violent heat; capable of récéiving fome impreflions “of 
“malleability, though ftill poffeffing exceffive biittlenefs'whén 
‘cold. The {pécific gravity ‘of iron’ thus united with oxygen is. 
6°5325. 
Thefe'ftates of extreme faturation’of carbon and oxygen 
only 
