_Welding._—The “welding” or “sparkling heat” is required in this process, which is a higher degree of heat than either named in the forgoing. In securing this heat, the metal is brought nearly to a state of fusion; which condition is made known by its sparkling, and presenting the appearance of being covered with a glaze, or a fresh coat of varnish. So soon as the two pieces of iron to be welded together have both attained to this necessary degree of heat, they are taken from the fire with the utmost dispatch, the scales or dirt which would hinder their incorporation scraped off, placed in contact at the heated point, and hammered until a union has been effected, and no seam or fissure remains visible. If the first effort fails to unite them sufficiently, they must be reheated and rehammered until the desired end is secured. The fire for welding should be free from sulphur; and the iron, while heating, should be taken out now and then and sprinkled over at the point of greatest heat with powdered glass, or with powdered borax. A small proportion of sand or powdered clay is sometimes mixed with the borax. These applications tend to prevent the iron from running or burning, and they are supposed to assist the adhesion when the two pieces are brought together in the act of welding. _Hardening Iron by Hammering._—Iron may be hardened to the character of a pretty fair spring metal by simply hammering it thoroughly while in a cold state. Many of the cheap spiral springs in use, as those attached to small bells for the purpose of imparting a vibratory motion, are hardened or stiffened in this way. They are first cut from soft sheet-iron and then hammered into the required hardness. Some heat to a cherry red and hammer to and after entire coldness. _Case-Hardening._—The various parts of gun mountings, such as guards, heel plates, etc., and the different parts of locks, such as hammers, tumblers, triggers and plates, as received by the gunsmith from the manufacturer or dealer in such articles, are generally in the rough or partially finished condition. Many gunsmiths, particularly those in the country, where there is more or less a class of cheap work, finish up these parts with a file and a little hand polishing, and when the work is put together hand it over to the customer. Not only tumblers and triggers, but even sears and tubes are finished up in this manner. As these parts are almost always made of soft iron, the result is they soon wear and have to be repaired. The gunsmith who does good work will thoroughly case-harden the parts when they are fitted and finished, and by so doing will turn out a really good piece of work that will wear as well as hardened steel. Why the majority of the trade do not case-harden their work cannot very well be explained, unless they are ignorant of the process or do not care to be put to the trouble of doing it. It is true it may be made a tedious job or a quick and easy one.