NEW YORK-CIUCAGO C.IBLE 



67 



to use butt-treated chestnut or cedar poles, or creosoted pine poles 

 where these prove to be the more economical. 



The galvanized steel suspension strand has a breaking strength 

 of about 16,000 pounds and the actual tension under normal condi- 

 tions is about 7,000 pounds. In placing the strand, it is necessary 

 to pull it to just the right tension in order that when the cable is 

 hung it will have the proper sag. The correct tension is readily 

 determined by what is known as the "oscillation" method. The 

 metal rings are spaced 16 inches apart and the cable weighs about 

 7>^ pounds per foot. 



The size and make-up.of the cable vary somewhat with the number of 

 circuits of the various types that are to be provided in the different 

 sections, but in general it is full size, that is, its over-all diameter is 



-Method of Supporting Aerial Cable and Messenger 



2^ in. which is about the maximum size of telephone cable. The 

 sheath is of lead-antimony alloy, one-eighth of an inch thick, and 

 under normal conditions it is, of course, air-tight to keep moisture 

 from entering. The cable for the aerial section was received from the 

 factory in 500-foot lengths, this being largely determined by the 

 arrangement necessary to permit the proper installation tests. 



Route 



We might next consider the route selected and for this purpose 

 Fig. 2 will again be helpful. It will be noted that starting at Phila- 



