Submarine cable laying and repairing

10 SUBMARINE CABLE LAYING AND REPAIRING,
left a back pull of 101b., tending to stop the wire paying out
further. The mean speed of descent was only about 65 fathoms
per minute.
The drum was made very light, of thin sheet galvanised
iron, to give it small inertia and prevent its shooting the wire
forward when the weight touched bottom. The auxiliary
pulley B for reeling-in was driven through speed-reducing gear
by the pinion A connected to the steam engine, and the wire
drum was driven by a band from B, a lever and tightening
gear being attached. The pulley C turned in any direction on
a centre coinciding with the horizontal portion of the wire, and
Wire Drum in position
for hauling in.
Fig. 7.—Silvertown Sounding Machine.
was therefore free to take up a position agreeing with any
direction in which the wire might stream out from the ship.
As the wire came up it was dried by passing through a block
of indiarubber and oiled by passing through a brush saturated
with lard oil, thus keeping it in good condition.
This machine is now superseded by machines adapted for the
use of heavier sinkers and greater speeds of descent. As the
moment of striking bottom can now be easily detected when the
line is run out at a speed of 100 to 150 fathoms per minute, it
not of importance to have the sounding machine drum of light
construction, and the system described above of adding weights