The Weight-per-mile-ohm

—A standard of primary winding of many turns is arranged conductivity used in comparing the relative | to lie within the groove of the secondary. Sliding clamps are provided in which the metal to be electrical resistance of various grades of | heated is held. The line pre ure may be reduced metals used in making wire. It is the, to one or two volts with proportional increase in weight of a conductor a mile long, and of | volume, which generates great ‘heat in the metal to be welded. i such uniform cro section as to have a resistance of one ohm. The greater the conductivity, the le is the weight-per-mile-ohm., The Welding, Electric.—The operation of weight-per-mile-ohm of pure copper is 859 lbs., | welding metals together by heating them, that is, a wire one mile long of pure copper and | having a resistance of one ohm weighs 859 lbs. while firmly butted together, by an electric current of great volume, and, as the Weight Voltameter.—A voltameter, such; metals soften at the contact faces by the as a gas or silver voltameter, in which the; intense heat, squeezing them together and amount of chemical change wrought by | shutting off the current.. the electric current is measured by weighing one or more of the products of the elec- Welding of Rails.—A method of joining trolysis. rails by welding them together, thus doing away with bolted joints.