This is the process by which 2 pieces of metal are joined together with the aid of heat. There are several forms of "weld." The principles upon which the welding of metals depends are here given. In welding generally, the surfaces of the pieces to be joined, having been shaped as required for the particular form of weld, are raised to a high temperature, and covered with a flux to prevent oxidation. They are then brought into intimate contact and well hammered, by which they are reduced to their original dimensions, the scale and flux are driven out, and the strength of the iron is improved.