172 Telephone Systems of the Continent of Europe 



OUTSIDE WORK (TRUNK) 



The wire used for the trunk line in France was at first 

 galvanised iron of 4 to 5 mm., but recently nothing but high con- 

 ductivity bronze or hard copper has been erected. This varies 

 from 3 mm. diameter on the shorter lines (Paris-Brussels, 320 kilo- 

 meters) to 5 mm. on the longer (Paris-Marseilles, 1,000 kilometers ; 

 and Paris- London, 501 kilometers). Trunk lines are crossed, not 

 twisted, but the non-use of cross-arms leads to the adoption of 

 clumsy and space-sacrificing devices. Fig. 56 represents the 

 crossing adopted on the Paris-Marseilles trunk. In the space 

 occupied by this single metallic circuit two or even three arms, each 



FIG. 56 



carrying six wires, could easily be got, and nine metallic circuits 

 obtained, each superior in symmetry to the Paris-Marseilles. In 

 Paris the trunk lines have to traverse considerable distances in the 

 sewers, the Paris-London having an underground course of this 

 nature of nearly eight kilometers ; but, thanks to the low capacity 

 of the Aboilard and Fortin-Hermann cables, no inconvenience 

 results. Many of the French trunks are worked simultaneously 

 as telegraph lines on the Van Rysselberghe, Picard, and Cailho 

 systems, but notwithstanding this, the speaking attains a high 

 figure of merit. 



