310 The N.Z. Journal of Science and Technology. [July 
transmission-line, which are symmetrically arranged with a spacing of 6 ft. 
between centres. The diameter of each conductor is 04 in., the height of 
B and C above the ground 32 ft. 2 in., the height of A above ground is 
37 ft. 5 in. The telegraph-wire D is assumed to be placed at a height of 
18 ft. above the ground, and to be composed of No. 11 S.W.G. wire, 
0*116 in. in diameter. 
The D.P. between phases is 66,000 volts, or 38,100 volts between each 
phase and neutral. 
Pig. 3 shows the maximum value to earth of the electrostatically induced 
E.M.F. in the wire D due to the impressed voltage mentioned in the 
power circuit for different distances between the vertical planes through 
A and D respectively. It will be seen on examination that the maximum 
induced voltage at 1 chain is 185 volts, at 2 chains it is 48 volts, whilst at 
6 chains it has fallen to 6 volts, subject in each case, of course, to large 
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disturbances in the event of unbalancing of the power circuits due to 
a short circuit on one phase, the magnitude of which depends upon 
the location of the fault and the nature of the short circuit; there is 
also a relatively smaller disturbance due to fluctuations of electro-motive 
force in the power circuits and the swaying of the conductors,- all values 
being calculated on the assumption that the telegraph-wire is perfectly 
insulated. 
The special case of a service telephone circuit carried on the same 
poles as the power wires remains to be considered. In the case of the 
Lake Coleridge line the telephone-wires, consisting of No. 8 galvanized-steel 
wires, are placed at a vertical distance of 6 ft. 5 in. below the plane of 
wires B and C, and 2 ft. 6 in. apart, symmetrically arranged one on each 
side of the pole. Considering one of these wires and proceeding to 
calculate the induced E.M.F. upon one of the telephone-wires, and calling 
this wire D as before, we have the following dimensions and distances, 
viz.: AD = 11 ft. 7 \ in. ; A'D = AD' = 63 ft. 3 in. ; BD = 6 ft. 8J in. ; 
B'D = BD' = 58 ft. ; CD = 7 ft. 7J in. ; C'D = CD' = 58 ft. 3 in. ; 
