be moved along the track as the work proceeds. The current to supply both the motors and the converters is taken from the line wire by the ordinary trolley arm. In making the weld the earth is removed from about the joint, clamps applied, and the current sent through the rail ends until these are brought to a welding heat.
Another method of utilizing the electric current in the working of metals shown by the Thomson Company is due to M. de
Fig. 9.—Tire Welder.
Meritens, a well-known French inventor and constructor of dynamos. This consists in forming an arc between the object to be heated and a movable electrode carried in the hand of the operator. In this case the work forms one terminal of the electric circuit and the hand tool the other. This hand tool consists simply of a stick of ordinary arc-light carbon mounted in a suitable holder, and connected with the circuit by a flexible cable.
The workman is by this simple device provided with a tool of remarkable range and flexibility. He has at his command the enormous temperature of the electric arc, yet in such a form that he can vary it from the heat of a taper to full intensity, and reach with it parts of his work that would otherwise be inaccessible.
