LINE WIRES. 



When a great length of wire is to be stretched between two 

 distant points without intermediate support, steel wire is often 

 preferred to iron, in consequence of its greater strength and 

 tenacity. 



Copper being a better conductor of electricity than iron, as well 

 as being less susceptible of oxydation, would on these accounts be 

 more eligible for telegraphic purposes. Its higher price, and the 

 possibility of compensation for the inferior conducting power of 

 iron, by using greater battery power, has rendered it preferable 

 to use that metal. 



47. Mr. Highton, the inventor of some important improvements 

 in telegraphic apparatus, affirms that, when galvanised iron wires 

 pass through large towns where great quantities of coal are 

 burnt, the sulphureous acid gas resulting from such combustion 

 acting upon the oxyde of zinc which coats the conducting wire, 

 converts it into a sulphate of zinc, which being soluble in water, 

 is immediately dissolved by rain, leaving the iron unprotected. 

 The wire consequently soon rusts, and is corroded. Mr. Highton 

 says, that in some cases he has found his telegraph wires reduced 

 by this cause to the thinness of a common sewing needle in less 

 than two years. 



The wires used on the American lines are of iron, similar to the 

 European, but are not galvanised. They soon become coated with 

 their own oxyde. A pair of galvanised wires have been placed 

 between New York and Boston, and I have been informed by Mr. 

 Shafiher, the secretary of the American Telegraph Confederation, that 

 at certain times during the winter, it has been found that they were 

 unable to work the telegraph with these wires, while its operation 

 with the wires not galvanised, was uninterrupted. Mr. Shaflher 

 also states that several anomalous circumstances have been mani- 

 fested upon some extensive lines of wire erected on the vast 

 prairies of Missouri. Thus, in the months of July and August, it 

 is found that the telegraph cannot be worked from two to six in the 

 afternoon, being the hottest hours of the day. These circumstances 

 are ascribed to some unexplained atmospheric effects. 



48. The manner in which the conducting wires are carried from 

 station to station is well known. Every railway traveller is familiar 

 with the lines of wire extended along the side of the railways, 

 which, when numerous, have been not unaptly compared to the 

 series of lines on which the notes of music are written, and which 

 are the metallic wires on which invisible messages are flying con- 

 tinually with a speed that surpasses imagination. These are sus- 

 pended on posts, erected at intervals of about sixty yards, being 

 at the rate of thirty to a mile. They therefore supply incidentally 

 a convenient means by which a passenger can ascertain the speed 



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