Page:Popular Science Monthly Volume 92.djvu/807

 Popular Science Munt/ilij

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��have only 6 causing a discharge. The net result is a pulsating charging voltage of 6.

The more skeptical of us might think that all of the current effective in charging comes from the dry cells and that the al- ternating current is not effective. But if we connect the dry cells to the storage battery, we have 9 volts charging against 6 tending to discharge, giving us an effec- tive charging potential of 3 volts or only half the value obtained with the alter- nating current arrangement.

With the connections shown, the charg- ing rate would be very low because of the high internal resistance of the batteries. Connecting several rows of dry cells in series parallel to provide the 9 volts would considerably hasten the charging. This method is recommended as a good one for use in connection with storage cells which have been sulphated, Bennett or Daniell cells taking the place of the dry batteries. The frequent alternations coupled with the low charging rate make for rapid cor- rection of the sulphation. — E. F. Hal- lock.

��Some Methods of Construction for Telephone Wires

AT the right side of the illustration Fig. 1 is shown a way of running a rural line along the top of a fence, the line v/ires

��being carried on insulators secured to the top of the fence posts. In the main part of Fig. 1 is shown how the wires are carried past a gate, and in Fig. 3 is shown how the wires are run through water-supply tunnels and large sewers; while Fig. 2 shows how large trees are sometimes used to support the wires and eliminate the cost of pole line construction.

When necessary to carry wires as shown in Figure 3, a regular lead-covered cable or an armored submarine cable is secured to the top of the tunnel or sewer by means of galvanized iron clips and brass screws which are driven into expansion shields. This method is generally used to supply service to a pump station or water intake which is situated out in the water some distance from the shore. When the water is quiet, as it is in a lake, the service is generally supplied by means of a regular submarine cable laid on the bottom of the lake; but when the cable must cross a swift-running river, it is advisable to put in the tunnel to prevent its being broken by the weight of water which would be constantly pressing against it.

In Fig. 1 the ends of the pipe coming up from under the driveway are bent down- ward at the ends to prevent water from entering the pipe during rainstorms or from the dew and rotting the insulation from the wires. — George M. Petersen.

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��Three methods of line construction to reduce the first cost, using a fence, tree or tunnel casing for supports

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