406 Telephone Systems of the Continent of Europe 



top, and closed by a disc of cast iron roughened at the top. 

 Figs. 145 and 145 A show the construction of the holes for the 

 road and footpath respectively. The cables are drawn in by a 

 capstan and iron wire having a breaking strain of 3,500 kilo- 

 grammes, rollers being temporarily fixed in the intermediate 

 manholes to lessen friction. The length drawn in at one time is 

 600 meters as a maximum. The cables used for the main routes. 



FIG. 145 



contain twenty-seven and fifty-two twisted pairs, the wires being 

 8 mm. gauge, loosely insulated with paper, so as to leave plenty 

 of air space. The protection consists of cotton yarn dried at a 

 high temperature ; then a leaden tube about 2 mm. thick ; 

 then a serving of jute tape impregnated with preservative com- 

 pound; and finally an armour of flattened steel wire laid on 

 spirally. Each flat wire has an external width of 47 and an 



