242 THE ADDRESSES, LECTURES, ETC., OF 



underground system of land telegraphy. When, in the year 1846, 

 the Prussian Government decided upon the construction of electric 

 telegraphs it adopted an underground system, which did not prove 

 practically successful, owing to a want of experience in insulating 

 the conductors, and in protecting them against the attacks of 

 animals and of gradual decay. The German Government, nothing 

 daunted by the comparative failure of these early experiments, 

 decided five years ago to resort again to the underground system 

 for the principal lines of communication throughout the country. 

 So complete has been their success that, after having laid down 

 some 8000 miles of underground insulated wire, they have resolved 

 upon a considerable further extension. The plan adopted in 

 Germany consists in enclosing seven or more insulated conductors 

 within a core of moist hemp, surrounded by a complete sheath of 

 iron wire, which again, is covered with a layer of hemp yarn, 

 impregnated with a protecting compound. These land cables are 

 wound upon drums at the sheathing works, and after being sub- 

 jected to careful electrical tests are paid out into trenches 3 feet 

 deep, and covered up. 



I may state, I think, without fear of contradiction, that on 

 these 8000 miles of underground wires, part of which have now 

 been down for five years, no expenditure for maintenance has been 

 incurred, and, judging by the perfect condition of the cables, it is 

 not likely that any repair will be required for many years to come. 

 Taking this immunity from decay and also from wear and tear into 

 account, I am convinced that the underground system is not only 

 the most perfect, but will also prove to be the cheapest in the end, 

 and an occurrence like that of yesterday furnishes perhaps a 

 fitting opportunity of calling, through your courtesy, public atten- 

 tion to this important matter. 



I am, sir, your obedient servant, 



C. WILLIAM SIEMENS. 



12, QUEEN ANNE'S GATE, January 19, 1881. 



