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POPULAR SCIENCE MONTHLY 



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 corro- 

 sion 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 at- 

 tacked, 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 



liEAD SkRVICK PiPK SHOWING THE luBEiiULAKll V OV I'^l.l.i I Jiul.Y 1 10 At Ilvi.N, uK WHAT IS 

 TECHNICALLY KNOWN AS " PITTING." 



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 phiu lias never been tried on a scale 

 large enough to afford a suitable demonstration of its utility. 

 AVhile it niight reasonably be tried on new construction, its ap- 



