The telegraph manual: a complete history and description of the semaphoric, electric and magnetic telegraphs of Europe, Asia, Africa, and America, ancient and modern.

560 TELEGRAPH INSULATION.
A straining screw and vice, shown in detail in the cut, fig.
70, are now secured on the post below the eye-bolts by the iron
arm, and both line rods are seized in the jaws of the double
vice, which is then screwed up by the winch, thus bracing the
wires two feet. The jaws of the stationary vice, through which,
previously loosened, the rods have moved freely, are now tightly
screwed together, so as to retain the rods while the main screw
and moveable vice are loosened and returned for another journey.
Fig. 70.
The portions of the rods between the moveable arm and the
post are now in loose loops between the post clamps and the
stationary vice. By relaxing one of the post side-screws, the
loop may be brought up so that it can be cut in the centre
between the side-screws, and each end be passed through the
eye-bolt resting on the groove at the top of the post.
A second journey of the bracing screw should now be made,
the portion of the rod gained secured, and the apparatus turned
in the opposite direction to strain on the other side. This
alternate straining should be carried on till the line is braced,
so that the lowest part subject to the strain shall be sixteen
feet clear above the ground.
Temporary props being now placed under the lines near the
straining post, this is removed. The ends of the rods are
turned into hooks on the eye-bolts, and an ingot of zinc is carefully cast over each hook, in the manner already pointed out.
The temporary props and scaffolding are now to be taken
away. This straining operation is to be performed as sparingly
as possible. Moderate curves on the line are not objectionable.
All that straining is required for is to elevate the lowest part
above sixteen feet from the ground. The application of the
straining apparatus once in a mile will be amply sufficient.