Evolution of Telephones 7 1 



underground in cables. Overhead lines 

 suffer in storms, and communication is 

 often broken down from this cause. But 

 even the cables are not free from trouble- 

 water is the greatest enemy, and if the 

 slightest crack develops in the covering 

 material, water will penetrate and interfere 

 seriously with transmission. Quite recently 

 a large exchange was cut off from London 

 entirely through storm water penetrating 

 the cable ducts. 



A cable will contain hundreds of wires, 

 in pairs, and in order that they may be 

 identified more readily, each wire has its 

 wrapping of coloured paper, the colours 

 arranged in sequence. The wires are then 

 covered with a waterproof insulating 

 material, and finally they are armoured with 

 a lead jacket. Earthenware pipes are laid, 

 these are called ducts, and through them 

 the long cables are pulled. 



Now come to the telephone exchange 

 the place with a thousand eyes which glare 

 at the stranger entering the large room of 

 mystery. Most of the eyes are white or 



