Switzerland 



407 



internal width of 4*3 mm., and is 1*7 mm. thick. The outside 

 diameters of the finished cables are 40 and 50 mm. respectively. 

 The copper resistance is 34-4 ohms, the insulation 5,000 megohms, 

 and the capacity '055 microfarad per kilometer, and the cable 

 stands a pull of eight tons with an elongation of only i per cent. 

 The maximum strain sustained in drawing in has been ascer- 

 tained not to exceed two tons, and the elongation to be only 

 3 per cent. Such a cable as this, if perfect to start with, once 



FIG. i45A 



properly laid, should remain serviceable for a long term of years. 

 Fig. 146 is an end section of a cable of this construction. The 

 underground work at Zurich already comprises ten kilometers of 

 conduits, containing eighty-two cables and 1,107 metallic circuits, 

 made up of 4,000 kilometers of single wire. The overhead wires 

 in Zurich still measure 5,200 kilometers. When certain sub- 

 scribers are connected, as much as six kilometers of underground 

 line is spoken through, the transmission being indistinguishable 



