Manual of military engineering . are kept well apart. Poles. 351. The poles may be of iron or wood, usuallv the latter. They should be buried in the ground to one-fifth their length,and their tops protected by a piece of galvanised sheet irontermed a pole roof. Arms. 352. ^Vhere more than one wire is carried on the same line of poles, the ^vires are attached to insulators fixed on wooden oriron arms, let into the pole, and at right angles to it (PL 89,Fig. 1). The length of the arm depends on the number ofwires to be carried. When more than one arm is required theyare usually placed at vertica
Manual of military engineering . are kept well apart. Poles. 351. The poles may be of iron or wood, usuallv the latter. They should be buried in the ground to one-fifth their length,and their tops protected by a piece of galvanised sheet irontermed a pole roof. Arms. 352. ^Vhere more than one wire is carried on the same line of poles, the ^vires are attached to insulators fixed on wooden oriron arms, let into the pole, and at right angles to it (PL 89,Fig. 1). The length of the arm depends on the number ofwires to be carried. When more than one arm is required theyare usually placed at vertical intervals of 1 foot. Earth 353. Wooden poles, except m dry rocky ground, should be wires. provided with earth wires, consisting of a piece of iron wirerunning down the pole, under the head of each arm-bolt to thebutt, where it is stapled in the f o^m of a small spiral; thisensures the earth ^vire being well under ground. Each of thearms is wired, and a turn of the wire is taken round the arm JP^ae^^ 89. TELEGRAPHS ar^thyxnj^e^.
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