Of all the metallurgical steel furnaces, the electric furnace is the most susceptible of accurate control. With the heat applied directly to the metal in the cleanest way possible, i. e., without the admission of coal ash or gas or air of the blast, the atmosphere in the tightly closed electric furnace can be made “oxidizing,” “neutral,” or “reducing” at will. The metal can be held in the furnace and additions made, samples taken, and the operations conducted with regulation and certainty. This newly devised metallurgical apparatus is coming to be largely used in the production of tool steels. While it has not displaced the crucible method for the production of steels of the very highest qualities, it has proceeded far enough in this direction in the very limited number of years since its introduction, that it is certain that the crucible, even for tool steels, is to have a keen competitor. Tool steels in considerable variety are to-day being quite satisfactorily made in the electric furnace and it is not at all unlikely that steels of the very highest grade will shortly be produced by this method. CHAPTER XIV THE ALLOY STEELS We have learned that steel, fundamentally, is an alloy of iron with carbon, i.e., carbon is the characteristic element. We are now to note what often seem to be exceptions to this rule. While in reality steel is just this iron-carbon alloy, there are alloys known as steels to which such strong characteristics are given by elements other than carbon, that carbon seems not to be the defining constituent at all. Indeed, in some of these, the carbon content may be small enough that, judging from our experience with the carbon steel series, we would not expect any such physical properties as some of these alloy steels show. You remember that in olden days they distinguished between wrought iron and steel by quenching the piece in water from a cherry-red heat. If the piece was hardened and made brittle, by this treatment, it was thereby proved to be “steel.” Also, it is generally known that by annealing a piece of hardened steel, which usually means holding at a cherry-red heat for a time and then cooling slowly, it is made soft. Then what shall we say concerning a certain one of these new alloys, Hadfield’s manganese steel, which is made very much less brittle and a little softer by quenching, but which refuses absolutely to soften under annealing treatment—in other words, is almost the opposite of what we know as steel in these chief defining traits? The nickel steel which contains 15 per cent of nickel, also, exhibits just these characteristics, being softened by quenching but not by annealing.