224 



METHODS OF COMMUNICATION FOR FOREST PROTECTION 



In handling- this wire the greatest care should be observed 1 to avoid kinks, bends, 

 scratches, or cuts. Joints should be made only with copper splicing sleeves and 

 connectors. 



On account of its conductivity being about five times that of E. B.B. iron wire, 

 and its breaking strength over three times its weight per mile, copper may be used 

 of which the section is smaller and the weight less than an equivalent iron wire, 

 allowing a greater number of ^ires to be strung on the poles. 



Besides this advantage, the reduction of section materially decreases the elec- 

 tro-static capacity, while its non-magnetic character lessens the self-induction of the 

 line, both of which features tend to increase the possible speed of signalling in tele- 

 graphing, and to give greater clearness of enunciation over telephone lines, especially 

 those of great length. 



TABLE 6 PROPERTIES OF BIMETALLIC WIRE 1 



Adapted from " Wire in Electrical Construction " by John A. Roebling's Sons Co. 



This wire consists of a steel centre with a cover of copper. Its conductivity is 

 about 65 per cent of that of pure copper. The percentage of copper and steel may 

 vary a trifle, hence the strength and weight must be approximate. 



TABLE 7 PROPERTIES OF GALVANIZED TELEPHONE AND TELEGRAPH WIRE. 1 



3 From American Steel and Wire Co. 



