658 PROCEEDINGS OF SECTION J. 



I may add that Mi'. Seitz explained to me only a few days agO' 

 some alterations and additions made by him since the date of the 

 Board's enquiry and which seemed to me to much increase the 

 value of the system. As he is applying for a patent for his system 

 I am not at liberty to mention the details. 



I think I have said enough to show that a great many 

 schemes of various kinds have been devised to try and satis- 

 factorily arrange for working wires carrying electric currents 

 under ground ; and when it is seen that not one has yet 

 been proved to have overcome the difficulties, it must be con- 

 fessed that these difficulties are very serious indeed. It has 

 been proved easy enough to work telegraph wires underground, 

 and telephone wires also, from any one place to any other ; but 

 after once laying down wires, the adding to them and tapping 

 them has been found to be the trouble. Then the electric light 

 wires present quite a different problem to overcome ; the current 

 they require to carry being so much larger and so much stronger 

 than that used on telegraph and telephone wires. The lead covered 

 cables which seem to be satisfactory for telegraph and telephone 

 purposes will not do for electric lighting. The conductors of the 

 lead coating separated by the insulating material are like the inner 

 and outer coatings of a Leyden jar, and sooner or later (particu- 

 larly where alternating currents are used) sj^arks pass from one to 

 the other and destroy the cable. What then are the essentials 1 

 First — wires must be insulated so that the current they carry 

 cannot escape to the earth or to each other. Then the material 

 used as an insulator must not be of high inductiA^e capacity, and 

 must be tough and lasting in quality. Next the wires and 

 insulation must be mechanically protected from injury. Then the 

 whole arrangement must be simple in construction and easy to 

 repair if it get out of order. There must be as few joints as 

 possible in wire, insulation, or protecting covering, and the wires 

 must be capable of being added to, or tapped for distribution 

 pux'poses. To comply with these requirements it has been, I 

 think, conclusively proved that if the wires are laid where they 

 are kept from light, and not subject to changes of temperature, 

 gutta percha is as good an insulator as any known substance. If, 

 however, they are to be laid loosely in a conduit, gutta percha will 

 not last any considerable length of time. 



It has been proved too, that the difficulties from induction 

 between wire and wire used for telegraph and telephone signalling 

 can be overcome by twisting the wires round each other into cables. 

 The induction difficulty with respect to electric light wires has not 

 been satisfactorily overcome. It has also been proved that iron is 

 the best material to protect the cables from injury under ground, 

 and that earthenware pipes are very unsatisfactory. 



It has also been proved that joint making in streets is so diffi- 

 cult that whichever system is adopted there must be no joint 



