130 ANNUAL OF SCIENTIFIC DISCOVERY. 



prosecution of telegraph lines through somewhat similar regions of 

 our own country : 



From Calcutta to Rajmoole, the conductor is laid under ground, in 

 a cement of melted resin and sand. From that village through the 

 remaining distance to Kedgeree it is carried ever ground on bamboo 

 poles, 15 feet high, coated with coal-tar and pitch, and strengthened 

 at various distances by posts of saul wood, teak and iron wood from 

 Ainerica. The bamboo posts are found to resist the storms which 

 have uprooted trees, the growth of centuries. Though the bamboo 

 soon decays, its amazing cheapness makes the use of it more economi- 

 cal than that of more durable and more costly materials. The branch 

 road from Bishlopore to Moyapore passes through a swamp ; the 

 country is little less than a lake for five months ; the conductor runs 

 on the foot paths between the island villages, and for some miles 

 crosses rice swamps, and creeks on Avhich no road or embankment 

 exists. 



The most difficult and objectionable line was selected to test the 

 practicability of carrying the conductors through swampy ground, and 

 it has been perfectly successful. The Huldee River crosses the Ked- 

 geree line halfway, and varies in breadth from 4,200 to 5,800 feet. 

 A gutta perclia wire, secured in the angles of a chain cable, is laid 

 across and under the river, and the chain is found to afford perfect 

 protection from the grapnels of the heavy native boats which are con- 

 stantly passing up and down. 



The overground lines differ totally from those in use in any other 

 country in this important respect. No wire is used. Instead of wire 

 a thick iron rod, f- of an inch diameter, weighing one ton to a mile, is 

 adopted the heaviest wire elsewhere used being only one cwt. to the 

 mile. The advantages of these substantial rods are these : they pos- 

 sess a complete immunity from gusts of wind or ordinary mechanical 

 violence ; if accidentally thrown down they are not injured, though 

 passengers and animals may trample on them ; owing to the mass of 

 metal, they give so free a passage to the electric currents that no 

 insulation is necessary; they are attached from bamboo to bamboo 

 without any protection, and they work without interruption through 

 the hardest rains ; the thickness of the wire allows of their being 

 placed on the posts without any occasion for the straining and wind- 

 ing apparatus, whereas the tension of wire exposes them to fracture, 

 occasions expense in construction and much difficulty in repairs ; the 

 thick rods also admit of rusting to take place without danger to an 

 extent which would be fatal to a wire ; and lastly, the rods are no 

 more costly than thin wire, and the Avoiding occasions no difficulty. 



The importance of this discovery of the superiority of rods over 

 wire will be fully appreciated in a country like In,lia, where the line 

 must often run through a howling wilderness, tenanted by savage 

 beasts or more savage men. The lines must therefore protect them- 

 selves, and this is secured by the use of thick rods. 



The entire expenditure on this line was about 450 rupees a mile, 

 and it is estimated that the future overground lines will be at the rate 



