UNDERGROUND ELECTRICAL WIRES. 655 



attempts were made to place wires in asphalte. Ten miles of such 

 a line was laid down in Paris at a cost of <£40 per mile per wire, 

 and the wires worked well for two or three years, but loss of 

 insulation finally was experienced ; the insulating compound 

 cracked and lost its qualities, particularly wliere exposed to the 

 action of gas from the street mains which softens it. Many experi- 

 ments were made before the plan which has been used for some 

 years past was adopted. 



In Paris, I need hardly say, there is a very complete system of 

 sewers, and the advantage of placing in them the telegraph wires 

 in addition to water and other pipes was naturally utilised. The 

 wires so placed are made up into cables. The conductors are 

 copper wires which are covered first with a coating of Chatterton's 

 compound and then with two layers of gutta pei'cha; tarred hemp 

 is wound round, and then seven of the wires are twisted into a 

 cable round which stout tarred hemp strand is wound, and finally 

 this is covered with strong tarred tape. Both the hemp and the 

 tape are steeped in sulphate of copper solution before being tarred, 

 and only the best Stockholm tar is used. Over all a coating of 

 lead is pressed and the cable is tlien hung in the sewer. 



Cables made in the same way but placed in iron pipes instead of 

 being lead coated ai'e laid (to some extent) underground. Great 

 care is taken both in the lead covered cable, and in that placed in 

 iron pipes to see that the lengths are pi'operly jointed together. 

 The lead joints are made as follows : — The copper wires are joined 

 and insulated in the usual way, and are then tightly wound round 

 with a broad band of stout vulcanized indiarubber, which is tied 

 round with yarn, tarred canvas is laid on over this, and tied also, 

 then a piece of lead piping about two feet long (which is slipped 

 on to the cable before the joint is commenced) is brought over the 

 joint and its ends pinched tightly round the sound cable. The 

 whole joint together with a few inches on each side of it, is wrapped 

 with tarred canvas closely bound on with galvanized iron wire. 

 The cost of this cable is from <£25 to <£30 per wire per mile, and 

 it is said to work well. I cannot find what the life of this cable 

 has been in France with any degree of certainty. I have found 

 frequent mention of failures, but whether they have been such as 

 to destroy the cable's usefulness altogether, I have not been able 

 to ascertain. One statement I met with in a French journal was 

 to the efi'ect that a lead covered cable placed in an iron pipe had 

 worked for twenty years. If so it has by far the best record of 

 any I have heard of. 



In America more than in any other countiy, the attention of 

 those interested in electrical conductors has been directed towards 

 finding a successful method of placing them underground. Wires 

 have multiplied more rapidly in America than elsewhere. So many 

 applications of electricity are used in the difierent cities, and the 

 telephone wires are more numerous in the United States than in 



