Werderman applied the high heat of the electric arc to melting and welding metals. His apparatus was an ordinary flaming arc, the carbons being inclined toward each other. The flame of the arc was directed away in a point from the carbons by means of a blast of air. In a more recent development by Zerener the repulsion of an electromagnet in series with the arc is used to direct the arc against the work. The following points have been charged against this process:

1. That it is much cheaper than either the oxy-hydrogen or oxy-acetylene flames; because the initial cost of the apparatus is lower and the cost of the energy used is less than the cost of the hot-flame gases for the same amount of work done.

2. That the flame is not easy to control.

3. That the flame is saturated with hot carbon and carbon gas from the pencils. The carbon is taken up by the molten metal, which becomes burnt or brittle.

4. That the intense light of the arc and the high voltage necessary make the welding rather dangerous to the operator.

5. That only a limited-sized flame can be obtained.

The Zerener arc has apparently never been tried out in this country. Abroad it is sometimes used for welding rough work, such as broken castings and pieces that do not need to retain any elasticity. In spite of its several limitations, the cheapness of operation should recommend it to trial.