_Tube Making._--Instead of heating strips of metal and welding the edges together, tubes may now be made seamless by rolling the heated metal around a solid heated rod; or by placing a hot ingot in a die and forcing a mandrel through the ingot. And as to tube and metal bending, there are wonderful machines which bend sheets of metal into great tubes, funnels, ship masts and cylinders. _Welding._--As to welding--the seams, instead of being hammered, are now formed by melting and condensing the edges, or adjoining parts, by the electric current. _Annealing and Tempering._--Steel wire and plates are now tempered and annealed by electricity. It is found that they can be heated to a high temperature more quickly and evenly by the electric current passed through them than by combustion, and the process is much used in making clock and watch springs. One way of hardening plates, especially armour plates, by what is called the Harveyized process, is by embedding the face of the plate in carbon, protecting the back and sides with sand, heating to about the melting point of cast iron, and then hardening the face by chilling, or otherwise. _Coating with Metal._--Although covering metal with metal has been practised from the earliest times, accomplished by heating and hammering, it was not until this century that electro-plating, and plating by chemical processes, as by dipping the metal into certain chemical solutions, and by the use of automatic machinery, were adopted. It was in the early part of the century that Volta discovered that in the voltaic battery certain metallic salts were reduced to their elements and deposited at the negative pole; and that Wollaston demonstrated how a silver plate in bath of sulphate of copper through which a current was passed became covered with copper. Then in 1838, Spencer applied these principles in making casts, and Jacobi in Russia shortly after electro-gilded a dome of a cathedral in St. Petersburg. Space will not permit the enumeration of the vast variety of processes and machines for coating and gilding that have since followed. _Metal Founding._--The treatment of metal after it flows from the furnaces, or is poured from the crucibles into moulds, by the operations of facing, drying, covering, casting and stripping, has given rise to a multitude of machines and methods for casting a great variety of objects. The most interesting inventions in this class have for their object the chilling, or chill hardening, of the outer surfaces of articles which are subject to the most and hardest wear, as axle boxes, hammers, anvils, etc., which is effected by exposing the red-hot metal to a blast of cold air, or by introducing a piece of iron into a mould containing the molten metal.