. The street railway review . had been stated that the tar coating is completely consumed and burntout by the lieat of the molten lead when a joint is poured, the writer causeda joint to be poured and calked in the usual manner, and then had thebell sawed into three pieces, so that it could be taken off the spigot. It isneedless to tell men who have had experience in laying and taking up watermains that the inner surface of the bell showed that the coating was entirelyunimpaired by the heat. Measurements were made by the writer in 1898 to determine the amount ofresistance offered by the joints
. The street railway review . had been stated that the tar coating is completely consumed and burntout by the lieat of the molten lead when a joint is poured, the writer causeda joint to be poured and calked in the usual manner, and then had thebell sawed into three pieces, so that it could be taken off the spigot. It isneedless to tell men who have had experience in laying and taking up watermains that the inner surface of the bell showed that the coating was entirelyunimpaired by the heat. Measurements were made by the writer in 1898 to determine the amount ofresistance offered by the joints in cast-iron water pipes, and also to ascertainwhetlier the pipes themselves showed any pitting as a result of this resistance. A large number of these examinations were made during 1898 and 1899, andin every case the pipe which was of the higher potential was found pittednear the joint, while the pipe of the lower potential, or that into which thecurrent was 6owing from the other pipe, showed much less electrolytic FIG. 8, To further test the joint resistance and to determine, if possible, the influenceof different methods of calking as affecting this resistance, the writer, in con-junction with Professor Jackson, caused a line of 6 and 4-in, pipe to be laidand supported on wooden blocks, so as to insulate it from the ground, asshown in Fig. 7. There were 27 joints in all. The pipe was new and hadnot been previously used. The calker was instructed to drive up the leadhard in one-third of the joints and to calk these joints in every way in thebest possible manner, just as though the pipe were expected to stand the heavypressure of the Peoria Water Works Cos. system. Another third of the jointswas calked not quite so hard, while the remainder were purposely only lightlydriven up. the work being done as though carelessly, or by a bungler. Acurrent of known strength was passed through the pipes, and the drop ofpotential around the joints was measured at points i ft. apar
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Keywords: ., book, bookcentury1800, bookdecade1890, booksubjectstreetrailroads
