THE ELECTRIC TELEGRAPH. 



under the foot pavements, along the sides of the streets, and are 

 thus conducted to the terminal stations of the various railways, 

 where they are united to the lines of wire supported on posts 

 along the sides of the railways, already described. 



66. Provisions, called testing posts, are made at intervals of a 

 quarter of a mile along the streets, by which any failure or 

 accidental irregularity in the buried wires can be ascertained, 

 and the place of such defect always known within a quarter of 

 a mile. 



144 



