Popular Science Munt/ilij 



791 



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. 



CUPPED TO BfSICK- 



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Three methods of line construction 

 to reduce the first cost, using a fence, 

 tree or tunnel casing for supports 



