Iron. 121 the ftate of gaz, which exhales and leaves the iron in a purer ftate. That kind of iron which contains an excefs of carbone, may therefore be improved or me liorated by ftirring it, while in the ftate of fu- fion/and while it is running out of the furnace; or it may be expofed for a longer time to the adfion of the bellows or blaft-work when melt ed, and the fmallcft quantity of charcoal made ufe of; tut when the two before mentioned principles are mixed in a due proportion with the iron, the call iron requires only the adtion of heat, to bring it to its proper ftate. When the calcining principle preponderates, the adtion of the bellows mud be lefs applied, and the metal mud be mixed or penetrated with a greater portion of charcoal, in order to carry off’ the fuperabundant portion of oxygen. Steel only differs from iron, as it contains a great portion of carbone, and hence arifes its being unalterable in fire when expofed to it in a vcffol excluded from the acceflion of pure air; but when repeatedly heated, and expofed to the atmofphere, it returns to the ftate of iron again. Some iron is malleable when red hot, but is brittle when cold; fuch iron melts eafier than the malleable kind, and its being brittle, is probably