CHEMICAL SCIENCE. 215 



opment of certain different colors under different degrees of heat, and by the 

 permanency of the action upon it of induced magnetism. It is distinguished 

 from pure iron by the complete absence in the latter of any one, or degrees 

 of any one of the properties just enumerated. But there are compounds of 

 iron that exhibit some, but not the whole of the special properties of steel. 

 The outer coating of common cast-iron when "chilled," or when the casting 

 has been made in sand, is often as hard and as untouchable by the file as 

 the best tempered steel itself. There exist, also, alloys of iron (as of iron 

 with manganese and other metals) such as those that were investigated by 

 Stoddart and Faraday, that in the property of hardness alone are scarcely 

 inferior to the finest steel. But in none of these special compounds are 

 there associated the whole of the peculiar physical properties, the collection 

 or series of which distinguish steel from any other substance. The peculiar 

 effects in modifying its normal properties of an admixture with steel, or 

 with pure iron, of phosphorus, sulphur, silicium, etc., are pretty well under- 

 stood; but it is the varieties of steel, the results of admixtures with steel 

 proper, of non-converted iron, in various proportions, that constitute the 

 real difficulties of discrimination, and for these there exists no special test. 



Place in the hands of an experienced steel-worker (a filemaker, a razor, a 

 watch-spring, a needle, or a surgical-instrument maker, for example), a 

 piece of rough, black, and unworked steel, part of a bar of cast-steel, for 

 instance, and ask him what metal it is. He will not judge of it by its 

 specific gravity, nor by application to it of nitric acid, or of any other chem- 

 ical test, but will proceed most probably as follows : He Avill balance it on 

 his hand, and, tapping it with a hammer, will bring out his " ring," as he 

 calls it, the peculiar intonation of which, Avhen steel, as compared with the 

 tone of iron, is, to his practised ear, a specific and infallible test of kind, and 

 almost exactly of quality. He will next make it red hot, and try how it 

 "draws; " that is, by repeated blows, will elongate the bar, watching as he 

 proceeds the texture of the metal, its adhesiveness, its flexibility, its indis- 

 position to scale, and the character of the marks inflicted upon it by his 

 hammer. When it is good steel upon which he is working, the sharp-edged, 

 well-defined impressions of his hammer's face (so finely developed, indeed, 

 as to reproduce even the grindstone lines that are left on the face of a recent- 

 ly-ground hammer), but when it is with iron or bad steel that he is work- 

 ing, then the shapeless and ill-defined impressions that result give to his prac- 

 tised eye all the information he seeks for as to the real quality of the metal 

 he is handling. Next he will try the temper of his forged specimen heat 

 it to some known degree, and, after dipping it in cold water, test its degree 

 of hardness by the file. Still, further, in proof, he will next fracture the 

 forged and tempered specimen, and, through its grain, find another evidence 

 of its character. If the fracture be a clean one, close-grained, compact and 

 silvery, it is steel; if ragged, fibrous, and leaden-hued, it is iron: or it will 

 be one or other of these, with such intermediate gradations as correspond to 

 all the differences in quality that lie between these two extremes. Next he 

 may polish its surface, and, gradually heating the specimen, he will, as the 

 temperature rises, watch that peculiar arrangement of colors, that, in their 

 special brilliancy, are peculiar to real steel alone : the assumption, first, of 

 various shades of yellow, deepening, as the heat increases, almost into 

 brown, then successively into greenish blue, with pure blue, and into purple 

 upon which there follows another kind of change a disruption of the 

 constitution of the metal, to which is due those play of colors and the oxida- 



