652 PROCEEDINGS OP SECTION J. 



There is little further to be said about the condition of things 

 in England. The mileage of telegraph wires placed underground 

 has continued to increase, but so far as I can learn nearly all the 

 telephone and electric light wires are overhead. The underground 

 wires are still in three-inch iron pipes, it having been satisfactorily 

 established that that size, with iron as a material, is much the best. 

 Engineers are not satisfied as to which is the best insulator and 

 various substances have been tried, among them asphalte has found 

 considerable favour and I find a method of placing wires in asphalte 

 thus described by Mr. Alexander J. S. Adams. Open up a trench 

 of suflicient depth and width, and in it lay a concrete foundation 

 and sides, two inches thick ; dress this concrete trough with hot 

 pitch, The trough should be carefully made. In it place a 

 diaphragm of wood, perforated with equi-distant holes ; pass the 

 copper wires through the holes and fasten them upon one side. 

 This board should be rigid. A second board, through the holes 

 of which the wires have been threaded, is carried along the trough 

 to a convenient distance and the wires .strained up by it. Hot 

 liquid asphalte, of a specially prepared kind, should then be poured 

 into the trough until level above the wires. A coating of hot pitch 

 is applied, and when cold the top dressing of concrete is raised 

 conically to resist downward pressure. The whole is then filled in 

 and carefully rammed with wooden punners. Wires laid in this 

 way lasted for three years, when they were taken up for some 

 reason or other. 



I find mention made by several other Telegraph Engineers of 

 trials with asphalte, but none very extensive, though all promised 

 well. 



I tried myself in a small way to similarly deal with a few wires. 

 It was as a temporary expedient, and was quite successful ; the 

 wires worked excellently buried in the asphalte. I think it is of 

 importance that only the best asphalte should be used. 



Paraffin wax has also been tried in England but it has not been 

 successful, owing chiefly to the fact that commercial paraflin and 

 copper do not agree together, an action being set up which 

 destroyes the insulation. 



Many compounds have been tried at difierent times most of 

 them being mixtures of earthy substances with gutta percha or 

 indiarubber. Lately wires have been insulated by having first a 

 coat of indiarubber or gutta percha, and being then covered with 

 twisted or plaited cotton saturated with parafiin. 



In France, Telegraph Engineers have ti'ied to lay wires under- 

 ground with more or less success. First, wires covered with gutta 

 percha and with India rubber were buried v.-ithout any metallic 

 protection outside the insulation. These did not last long. Then 

 similarly treated wires were drawn into a lead pipe, and laid down. 

 These did not last very long either, for gas got in through the 

 joints of the lead pipe and destroyed the gutta percha. Then 



