Undoubtedly the smith's art is of great antiquity, and it is sometimes a question why the early artificers in metals should have blended copper and tin, during the bronze period, before creating what the author might term a welding period. Doubtless the requirement of a high temperature, created by a blast, was the impediment, for it is related that one of the earliest productions of this very necessary accessory to the smithy was the selection of a valley, with known prevailing winds, then boring two or more cone-shaped tunnels thorough a lull, with the bell mouth to the wind, and tapering them to meet in one narrow neck. The ancient smith also appears to have been a factor of great power among the armies of his day, for upon him the conquering made special raids, in order that the vanquished should be without the means of reproducing those wonderful blades, which cut that which offered no resistance, and consequently remain for a longer period under submission. The author is fully aware that this is probably of more interest from an archaeological point of view than mechanical, and he offers the most beautiful and wonderful work of the early English smith, such as the fabrication of most costly armour and the production of ecclesiastical ornamental work, as his apology for introducing such remarks to his readers.

It is somewhat difficult to draw a definite line of demarcation between the forge and smithy work, consequently the section devoted to the forge should be read conjointly with the present one, because in many cases the former has to prepare rough forgings for the latter, and active management is always working in the direction of saving as much of this class of work as possible, consequently the larger and heavier portions of smithy work are constantly being devised - by the aid of more complete tools - to be finished in the forge for the machine shop; therefore for this reason and the use of steel castings, Section II., Part II., page 72, the smith's work is being periodically curtailed.

Wrought iron is the material upon which the smith is generally engaged, but mild steel, both acid and basic, is now being extensively used, and, after a little experience, it is a fact that a smith will prefer the latter, especially if the former has been produced from inferior scrap, or from scrap that has been worked a number of times, or is red-short. The relative qualities of the various brands of wrought iron may be pretty accurately gauged by a comparison of fractures, provided they have all been broken under similar conditions, a ready means being to nick and bend across the anvil. It is obvious that for comparison the conditions must he similar, because the fracture produced by a tensile strain will be vastly different from that produced by bending. The texture of good wrought iron is fine and close, and of a silver grey colour. It is well exemplified by nicking a 1¬ inch bar about « inch deep, and then bending the sample down flat upon itself, when the fibre will be found to be quite distinct and long, whereas inferior iron may be coarse and granular, with short fibre of a dark colour, indicating cold-shortness, and sometimes largely crystalline. It is certain that the element of time will affect the fracture, and to bring out the fibre thoroughly, the bending operation should be performed slowly and gradually.

The principal operation with which the smith is concerned is welding, which gives to iron its great intrinsic value, and is generally considered to be an adhesion under pressure of two pieces, which have been heated up to the plastic limit. Practically the two are made into one, but the great difficulty in removing dirt, scoria, oxide or other foreign matter, renders an actual and perfect contact almost impossible; and however good a weld may be, and whatever attention may have been bestowed upon its production, a line of demarcation may generally be detected. A fine metallic surface is of course the first requisite, followed immediately, and of equal importance, by a consideration of the impurities incorporated in the iron. These impurities will affect the weld by their own weldability, and their tendency to crystallisation, also if prone to oxidation to a greater degree than the iron in which they are, they must naturally be taken as detrimental. Their weldability may be dispensed with, by stating that there are only two impurities, viz. nickel and cobalt, which will weld, consequently all others must be taken as hurtful. The property of retaining an amorphous or plastic condition up to a high temperature, say approaching its melting point, is favourable to good welding; therefore, anything that tends to lower this condition, such as carbon, silicon and phosphorus, causes the resulting weld to bo of an inferior quality, generally known as being coldshort. These impurities are not actually detrimental to the act of welding, but lower the welding temperature, especially in the case of phosphorus. Sulphur behaves differently, it aids the separation out of the more fusible compounds; consequently, iron containing it crumbles when struck.

Manganese in high percentages causes the material to be very red-short, and the greatest care is required both in the gradual heating and ultimate manipulation; nothing but the lowest temperatures will permit of the working of a material high in manganese in any degree. Therefore, to produce a sound weld, there must be the fullest contact between the un-oxidised metallic surfaces of the metal; and the more homogeneous and pure the material is, the more perfect will be the weld. It is difficult without hammering to bring these surfaces into sufficiently near contact, and also to remove the slag which has been developed to prevent the oxidation of the scarf whilst heating. It is more difficult to weld mild steel or ingot iron, because it requires a quick fire and smart handling, success depending to a greater extent upon the mechanical treatment than chemical composition. It will not weld nearly so well as iron containing a greater percentage of impurities, because in the latter they partake more the nature of an admixture than a chemical combination; and it is found from considerable experience that the welding heat for mild steel is at the point of transition from a bright red to a white heat, which appears to be the temperature, when, as it were, the cohesive state is changed for that of the plastic.