The Sun.
London, England, 1865-05-30 00:00:00

The Atlantic Telegraph.

Yesterday the last mile of this great cable was
completed, and wound through the last of the cover-
ing machines, in the presence of a large number of
distinguished visitors who had assembled to do
honour to the occasion. Beyond recording the fact
of its completion, very little took place at the works
of the Telegraph Company yesterday to call for
special remark. All the most distinguished electri-
cians and engineers, and all the leading scientific
gentlemen who had so long watched and aided to
the utmost of their power the promotion of this
great scheme, were present ; together with all, or
nearly all, the directors of the Telegraph Mainten-
ance Company, Mr. Glass, as usual, receiving the
visitors. As a mere sight there was, of course, very
little to be witnessed—much less, in fact, than
might have been seen at the works any day this
twelvemonth past. Only one machine had half
a mile to complete—that is to say, to case the
core with Mr. Wright's most ingenious and simple
patent of wire enclosed with strands of hemp
which form the outer covering. When all the
visitors were assembled this was started, and the
core wound regularly and slowly through the centre
of the machine, which, revolving round at a great
speed, completed the outer case of hemp and iron.
Working at 14 hours a day, each machine is able
thus to cover four miles an hour, the average rate of
manufacture for the four machines having been
about 17 miles per day. As the cable is drawn out
of the machine it passes through a gauge, which
compresses it firmly, and then out of the manufac-
tory away to the tanks, where it is coiled under
water, and every change in its electrical condition
noted with a care and minuteness that have cer-
tainly never yet been applied to any other cable.
From first to last, indeed, it has been subjected to a
series of the most searching electrical tests, the
standard of insulation being fixed at a resistance
per nautical mile equal to 150,000,000 of Sieman's
units, at a temperature of 75 degrees—a standard
wholly unprecedented in any former work of the
kind. In actual practice these tests, great as they
were, have been considerably exceeded, and the pre-
sent Atlantic cable has come out successfully from
a series of trials of the most crucial character. The
results which have been obtained have been due
mainly to the searching investigation into the quali-
ties of insulating substances which is now practicable
by means of the beautiful mirror galvanometer of
Professor Thompson. Another of the tests em-
ployed was soaking separately each joint of the
gutta-percha covering for 24 hours in warm water
previous to passing the electric current through. A
third, and perhaps the most trying and continuous
test, was that of allowing no part of the cable to•be
out of the water, except while merely in transitu
from one reservoir to the other ; and in connexion
with this it may be mentioned that the wrapping
of jute yarn, which forms the padding around which
the external wires are spun, instead of being
soaked in tar, as in other cables, which has the
effect of temporarily stopping up and concealing
minute flaws, has been simply tanned to preserve it
from decay, thus admitting the water to search out
every part of the cable, and keep it, in fact, con-
stantly surrounded with a wrapping of wet yarn.
Towards 5 o'clock yesterday the last few fathoms
of the great coil began to be drawn into the machine,
and in a few minutes after the end was wound up a
self-acting bell rang to give notice that the machine
was empty, and almost at the same moment the
end came down into the tank, and the last coil of
the cable was stowed away. The next great object
of interest was the inspection of the paying-out ap-
paratus, which has been already fixed up, and, by
means of an endless band, kept constantly running.
This beautiful machine is an improved and extended
copy, as far as general principle is concerned, of
that used on board the Agamemnon during the first
memorable attempts. Its improvements and modi-
fications, however, are very great. Though stronger
and much larger, it is very much lightei, being
made almost entirely of wrought-iron. It has six
leading wheels, round which the cable. passes in deep
grooves before reaching the main wheel or drum,
from which it will be finally submerged. Each
groove in these six wheels is surmounted by what
is termed a jockey-pulley—that is to say, a solid
wheel, which keeps the rope down in the groove
and prevents it over-riding or getting out of place.
The main drum is about 7ft. diameter, and in pay-
ing out will have three coils of cable round it, with
a guiding piece of wrought-iron pressed on them
sideways to keep them compactly together. As the
friction on the guider is great and constant a
duplicate is provided in case of heating, which can
be put in gear with the rest of the machinery
without the slightest stoppage of any part. A
second drum has also been fitted in case of any-
thing going wrong with the first. Each of these
drums is fitted with a distinct set of simple and
most ingenious brakes, invented by Mr. Appold
for the first expedition. The ordinary condition of
these brakes is to maintain a sufficient check upon
the drum to keep a strain of say 30 cwt. or 40 cwt.
upon the rope going out, but it constantly happens
that a sudden rise of the ship's stern from a wave
gives the cable a strain that requires instant re-
moval of the brakes to relieve it. This is accom-
plished by a dynamimeter placed On the cable after
it leaves the paying-out machine and before it passes
over the Ni heel astern into the Atlantic. This dyna-
mimeter is only a heavy wheel resting on the rope,
but fixed in an upright frame, which allows it to
glide freely up and down, and on this frame are
marked the figures which show exactly the strain in
pounds on the cable. Thus, when the strain is low
the cable slackens, and the dynamimeter sinks low
with it ; when, on the contrary, the strain is great,
the cable is drawn " taut," and on it the dyna-
mimiter rises to its full height. When it sinks too
low, the cable is generally running away too fast,
and the brakes have to be applied to check it ;
when, on the contrary, it rises rapidly the tension
is dangerous, and the brakes have to be almost
opened to relieve it. The simplicity of the appara-
tus for opening and shutting the brakes is the most
beautiful of all. Opposite the dynamimeter is
placed a tiller-wheel, and the man in charge of this
never lets it go nor slackens in his attention for
an instant, but watches the rise and fall of the dy-
namimeter as a sailor at the wheel watches his com-
pass. A single movement of this wheel to the right
puts the brakes on, a turn to the left opens them. A
good and experienced brakesmanrwill generally con-
trive to avoid either extreme of a high or low strain,
though there are few duties connected with the
laying of submarine cables which are more anxious
and more responsible while they last than those
connected with the management of the brakes.
The whole machine yesterday worked beautifully,
and with so little friction that when the brakes were
removed a weight of 200 lb. was sufficient to draw
the cable through it.
In order to guard against any possible sources of
accident, every preparation has been made in case
of the worst, and, in the event of very bad weather,
for cutting the cable adrift and buoying it. For this
purpose a wire rope of great strength and no less
than five miles long, having a distinctive mark at
every 100 fathoms, will be taken in the Great
Eastern. This, of course, is only carried in case of
desperate eventualities arising, and in the earnest
hope that not an inch of it will ever be required. If,
unfortunately, its services should be wanted, the
cable would be firmly made fast to its extremity,
and so many hundred fathoms of the wire rope
according to the depth of water the cable was in
measured out. To the other end of the rope an im-
mense buoy would be attached, and the whole then
cut adrift and left to itself till better weather. In
the experimental cruises which were undertaken
before the starting of the last Atlantic expedition
this attempt at buoying the cable was often tried in
the deep water of the Bay of Biscay, but never with
any great success, and in very deep water it would
be a most forlorn hope indeed to try it at ail.
After going all over the works yesterday, and in-
specting all the apparatus, the visitors left the

buildings shortly before 6 o'clock, and were enter-
tained by the directors of the Telegraph Company
at a banquet at the Ship at Greenwich, when " Suc-
cess to the Atlantic Telegraph" was drunk with the
utmost enthusiasm.