_Welding Steel._—The common method employed for welding iron to iron is often resorted to for welding steel to steel, but a great deal more care is necessary to success in the latter than in the former case. There must be much precision so far as relates to the rate of heat, as the margin for variation is extremely small. If the temperature is not high enough there will be no adhesion, of course; and if it attains to only a few degrees above what is actually necessary, the steel either “runs” and is ruined, or is ruined by going into an unworkable condition known as “burnt.” It sometimes becomes necessary to weld steel and iron together; this may be effected by the same process as that employed in welding steel to steel. None but workmen of thorough experience would be apt to succeed in either case, on the old plan of proceeding the same as in welding iron to iron. But steel may be more easily welded than on the old plan by the employment of certain welding compositions. One of them consists of half a pound of saltpetre dissolved in half a pound of oil of vitriol, and afterwards added to two gallons of soft water. Heat the pieces to a cherry-red, then plunge them into this composition; after which proceed to reheat and weld in the usual way. At the welding the strokes of the hammer should be quick and light. Another composition is made by pulverizing together ten parts of borax and one part of sal-ammoniac. Thoroughly melt the composition so made in an iron pot, then pour out upon some level surface to cool. When cooled grind to a fine powder. Heat the pieces of steel and sprinkle this welding powder over them; then return to the fire, and again heat up, and it is ready to go together under the hammer. Some smiths claim to weld steel successfully by dusting over the heated pieces a powder composed of clear white sand, 2 lbs., and plaster of Paris, 1 lb.; then reheating and proceeding in the usual way. In welding steel to iron the foregoing processes are employed the same as if both pieces were steel.