212 METHODS OF COMMUNICATION FOR FOREST PROTECTION 



cotton wrapping, shall not act injuriously thereupon, and shall be insoluble in water. 

 The compound shall adhere firmly to the cotton covering and shall not drop or run 

 when the finished wire is subjected to a temperature of 150 F. for thirty minutes, 

 and shall not crack when the wire is subjected to a temperature of 10 F. for thirty 

 minutes. 



The diameter of the completed wire shall not be more than -048 in. and not less 

 than -043 in. 



Spooling, The wire shall be evenly wound on wooden spools weighing approxi- 

 mately three-quarters of a pound. 



The inner end of the wire shall be brought out through the spool head. 



The length of the wire shall be 2,640 ft. plus 100 ft. 



The exact length of the wire shall be marked on the spool. 



The wire on each spool shall be one continuous length. 



Splices. Spliced joints shall be equal to or stronger than the wire itself and 

 shall be so made as not to materially increase the diameter of the conductor at the 

 point where the splice occurs. 



Weight per mile. The weight per mile of the finished wire shall not exceed 

 nineteen and a half (19-5) pounds and shall not be less than seventeen and a half 

 (17-5) pounds. This does not include the weight of the wooden spool. 



Tensile Strength. Tests shall be made on wire from the ends of which the insula- 

 tion has been removed. The finished wire shall have a minimum breaking weight of 

 forty-five (45) pounds and a minimum elongation of one-half of 1 per cent in a length 

 of 2 feet. 



Resistance. The resistance of this wire shall not be more than 60 ohms per mile 

 at a temperature of 68 F. 



5 Specifications for Rubber-covered Copper Wire 



General. The quality of the material used must be of the best, and the manu- 

 facture, workmanship, and finish must be in accordance with the best commercial 

 practice. 



Manufacture. The conductor shall be in one continuous length, cylindrical in 

 section, and uniformly drawn, so that the variation over or under the specified 

 diameter shall not exceed one (1) mil (one one-thousandth of an^ inch). It shall 

 be uniform in quality, free from factory joints, scales, splints, flaws, and other 

 imperfections. To ensure the removal of defects from the conductor the manufac- 

 turer shall cut off 2'5 ft., or ,as much more as may be necessary, from each end of 

 every coil. 



Each conductor before being insulated shall be thoroughly and uniformly linned. 

 The tin coating nost conform to the following requirements: The tinned conductor 

 shall be immersed in a current of pure hydrogen sulphide gas, saturated with water 

 vapour at a temperature of not less than 75F. and not more than 79F. for four 

 hours. At the end of this time the conductor must exhibit no signs of blackening. 



Insulation. The tinned conductor shall be evenly and smoothly covered with 

 vulcanized rubber of the best quality, which is impervious to moisture, or some other 

 approved weather-proof, insulating compound to such a thickness as hereinafter 

 specified. 



The dielectric shall adhere firmly to the conductor and shall not act injuriously 

 upon it. The wire shall be well centred in the dielectric. The dielectric shall not 

 soften sufficiently to allow decentralization at a lower temperature than 130 F. 



