5gO PHILOSOPHICAL TRANSACTIONS. [aNNO ITQS. 



2. Steel has composition. It is a compound of iron and carbon, the propor- 

 tions of which have not been accurately determined, but may be estimated to be 

 one of carbon and 300 of iron. I would call this state of iron from external pro- 

 perties, hard malleable iron : and from interior structure and composition it may 

 be called, as in the new system, carburet of iron. Steel of the best imaginable 

 kind is that which has not yet been manufactured : for it is that which has the 

 most extensive range of degrees of hardness, or temper ; the greatest strength, 

 malleability, ductility, and elasticity ; which has the greatest compactness or 

 specific gravity, and which takes the finest polish ; and lastly, which possesses 

 these qualities equally in every part. Steel made by cementation, of the best 

 quality, which has been melted, approximates the nearest to this kind of steel. 

 Its greatest defect is want of malleability. 



3. Crude or raw iron is a mixture, and has composition. It consists of pure 

 iron united, and mixed with other substances so as to be hard unmalleable iron : 

 but the substances with which it is almost always mixed and united, are 3, viz. 

 oxygen, carbon, and earth. I would term this state of iron, on account of ex- 

 ternal properties, hard unmalleable iron ; and on account of structure, impure 

 iron. In this statement of the interior structure of the different states of iron I 

 have not thought it necessary to reckon the impalpable fluids, which they con- 

 tain in perhaps different proportions ; viz. light, caloric, electric, and magnetic 

 fluids : for I believe their chemical agency has not been ascertained. 



Iron may also contain a much greater quantity of carbon than has been above 

 stated to be a constituent part of steel; and this state of iron is hard, unmalleable, 

 and is not uniform in its texture. It may be called, according to the new no- 

 menclature, hyper-carburet of iron. It is liable to be produced by cementing 

 iron in a very high temperature for a very long time, with a large quantity of 

 carbon ; and it is also produced by melting iron, or steel, with carbon. 



There are innumerable varieties of the first explained state of iron, viz. wrought 

 iron. Some of these are familiarly known and distinguished by names among 

 artists. Difterent quantities of carbon, which is here an impurity, are the oc- 

 casion of these varieties ; but as the carbon is not in sufficient quantity to dir 

 minish the toughness, softness, and malleability, to such a degree as to produce 

 the obvious qualities of steel, such varieties are reckoned to be those of wrought 

 iron. The carbon may however be in such proportion as to produce a state of 

 iron, which in some degree possesses the properties both of steel, and wrought 

 iron ; or which possesses partly the properties of steel, and partly the properties 

 of wrought iron. It is quite arbitary to call such kinds of iron, steel or wrought 

 iron. 



There are also innumerable varieties of the 2d state of iron explained, viz. 

 steel. Some of these are known and distinguished by artists. A greater or 



