Page:Popular Science Monthly Volume 56.djvu/376

362 tempting a greater flow of electricity along other paths than the rails and track feeders. It has been generally believed that this increased current would develop electrolysis at the ends of the pipes, due to the jumping of the electricity around the presumably high resistance of the joints; and, indeed, many samples of such corrosion are in existence. I have found, however, that it is possible to calk a bell-and-spigot joint in cast-iron pipe in such a manner that the resistance is practically nil; and as for wrought iron or steel, the joint resistance may be made as low as we please by fitting the surfaces so carefully that white-leading is unnecessary. Arguing from the fact that the negative electrode is not attacked, it has been suggested to employ an auxiliary dynamo and a special system of wiring, in order to maintain the pipes, etc., at all times and at all points, negative to the rails. Could this ideal condition be realized, the rails alone would suffer. We can not



hope, however, to thus easily solve the problem in towns where the distribution of buried conductors is at all complex.

It has been suggested, also, to discourage the flow of electricity along pipes and cable covers by inserting insulating sections of wood or terra cotta. This plan has never been tried on a scale large enough to afford a suitable demonstration of its utility. while it might reasonably be tried on new construction, its