The Sun.
London, England, 1864-11-12 00:00:00

The Atlantic Telegraph.

The manufacture of the cable for the Atlantic Telegraph
has now made such progress that the time of its comple-
tion may be calculated to a day, and should all go well in
the submergence of the line, there appears no reason why,
by the end of July, 1865, there should not be telegraphic

conratunication between England and the American con•

tinent. And, if the same amount of care and foresight
is shown that is at present bestowed upon the manufacture

of the cable, it would seem that auceess is certain and

assured. Any person who was acquainted with the manner
in which the first cable was prepared—the inferior quality
of its materials and the ill-usage to which it was subjected
must be struck with the great contrast now exhibited in
these points—and if with all these drawbacks, and with the

limited experience of our electricians, the feat was accom-
plished of transmitting messages to and from America,
there would appear no reason why, in the completely al-

ered state of circumstances, a grand and decided success

should not be achieved.

The Government have not, as on the former occasion,

given to the enterprising company the use of one of their

first-class frigates, such as the Agamemnon; but they have
lent to the company two old war ships—the Amethyst and

the Iris, which have for years past been on the sick and dis-

abled list in the Medway, and which will convey the cable,

as it is completed, from the works at Greenwich to the
Great Eastern at Sheerness, Tho Amethyst is now lying
in the river off Greenwich, and a portion of her deck is in

°ours° of removal, in order to take in the iron tanks in
which the cable will be coiled. The one great feature of
difference in the manufacture of the present and the former

cable is that while the one was not in water until it was

[aid in the depths of the Atlantic, the other will not be out

of the water from the time of the first stage of its progress
until it is deposited in its ocean bed. This affords opportu.
nity for conducting a continuous series of electrical tests
under circumstances best calculated to discover any defect
in the construction. It involves, however, a very large
expenditure. In the first place, there are six circular
iron tanks or reservoirs, about thirty feet in dia-
meter, and about twelve feet deep, erected at the
works of the Telegraph Construction and Maintenance
Company, at East Greenwich (formerly Glass, Elliot, and
Company). auto these the cable is coiled as it is formed,
and every fresh layer of the coils is submerged with water,
Each of these tanks will hold more than 120 miles of the

cable. Then there are four similar tanks, but considerably

larger, to be built and fitted, two each, in the Amethyst and
Iris; and when the cable is removed into them it will here
also be laid under water. There are yet three more tanks,
each nearly double the size, or 58 feet in diameter, to be put

together on board the Great Eastern, into which the cable
will be coiled from the conveying ships, and, as in the for-
mer stages, the wire will be under water. No small part of
the outlay required for the work will be taken up in this
preliminary stage of finding the means of storing the cable
while in process of manufacture and en route to its destina-
tion. When all is complete, and the signal is given to the
Great Eastern to go a-head, she will have a load, including
fuel for the voyage and paying-out apparatus, of 17,000
tons, and of this the weight of the cable alone will be

3,960 tons, or, including tho tanks and the water, not
ar short of 5,000 tons; and if the weather be favourable

and all goes well, the line will be laid in about twelve days.
With respect to the cable itself, that is a subject which
has occupied an immense amount of attention, first in
deciding upon its proper form and constituents, and next in
securing tie requisite quality of materials and workman-
ship. Upon the first point the directors of the company
very wisely resolved that they would not, as was the case on
the former occasion, take on themselves the responsibility
of deciding on a subject of which they were profoundly igno•
r ant, and they left it to a committee, consisting of Mr Fair-
bairn, Mr Whitworth, Capt. Gahm], Prof.'\Vheatsone, and
Prof. Thompson, to determine the conditions which, after
mature deliberation and experiment, they considered re-
quisite. One of the difficulties which the committee had
to solve wr.-3 so to arrange the various parts as to prevent
any strain upon the core, or portion along which the
electricity has to pass. There are some portions of the
Atlantic where the depth is more than two and a half miles,
and the mere weight of such a length of cable as would
extend from the bottom of the ocean to the ship would

be sufficient, unless proper precautions were taken, to
stretch or to break this inner wire. The line as first
constructed failed in consequence of this point not having
been kept sufficiently in view—its specific gravity was much
too great for its strength, and it was the strain upon the
inner corn which was, probably, the cause of its failure.
The new cable, like the first one, has a centre or core formed
of 7 copper wires-6 laid round one. The weight of copper
in these wires is, however, 3031 b for each nautical mile, as
against 1061 b in the first cable. This is in itself an impor-
tant point of difference, the weight of copper for the con-
ducting wires in the whole length being more than 200 tons
greater than in the first cable. The gauge of the wire used
is that known as No. 18. These conducting wires are in-
,ailated by four layers of gutta percha, laid on alternately
with four thin layers of the material known as Chatterton's
compound, the diameter of the core thus covered being
rather less than half an inch,tho exact figures being '464in,
and the circumference 1.39 tin. In the first cable the core
was protected by three coverings of gutta percha, weighing
2,311 b per nautical mile—the difference between the nautical
and geographical mile is in the proportion of 2,126 to 1,760
yards—te weight of the insulator in the first cable was
2611 b, in the present one it is 4001 b per mile. For the pro-
tection of the core and the insulating portions there is a
padding or coating of soft jute yam, saturated with a pre-
servative mixture, which is wound round and next to the
insulating outer surface of gutta percha. This will help
to resist the strain brought to bear upon the cable when a
great length ;s paid out in deep water. Outside of this
padding is the coating, employed only for protective pur-
poses, and forming, of course, no part of the telegraph pm-
per. This consists of ten solid wires, of the gauge .095,
drawn from homogeneous iron. Each of these wires is
surrounded separately, with five-strand tarred manilla.
The whole of these ten strands are then laid spirally round
the padded core, and they are formed in such a manner
that when a heavy strain comes upon it the wires will
give greater strength to the cable. In the first telegraph
the protection of the core was sought to be effected by
eighteen strands of charcoal iron wire, each strand com-
posed of seven thread• like wires. These were laid spirally
round and upon the core. In paying out the cable the
whole strain came upon the core, or inner portion,
and "not upon this outer coating of wire, which really served
only to increase the specific gravity without giving addi-
tional strength. The line now in hand has a vast superiority
over the former one in regard to its specific gravity. The
first weighed in air 20cwt , this weighs 34cwt to the nautical
mile ; in water, however, the weight of the first was 13.4 c w
per mile ; the specific gravity of the second, notwithstand-
ing its greater strength and increased diameter, is but 14cw t.
When it is considered that probably some eight or ten miles
of the cable will be suspended in water between the points
on which it rests at the bottom of the ocean and the ship
from which it is being paid out, it will be seen at once how
important is this great increase of strength, obtained as it
is with so small an addition to its specific gravity. Buoyancy
combined with strength has been obtained in a very satis-
factory manner. The hemp which surrounds the protecting
covering of the iron wires is much lighter than water,
hence the comparatively low specific gravity. The next
important point is the strength or breaking strain. This
in the first telegraphic cable was 65cwt, in the present it is
155 cwt, or considerably more than twice that of the for-
mer.

The first stage in the manufacture is carried on at the
works formerly of the Gutta Percha Company, near the
City-read, but which are now incorporated with the firm
of Glass, Elliot, and Company, under the name of the
Telegraph Construction and Maintenance Company
(Limited). There aro seven copper wires to form the con-
ductor• The entire length of the telegraph will be 2,303
miles, so that there is 16,000 miles of copper wire. Every
portion of this copper wire is subjected to electrical tests
to ascertain its quality for conduction before it is allowed
to be worked up. The next stage is to coat these wires
with eight successive coats of the insulating material,
equal to an aggregate length of 18,400 miles. This core is
next covered with jute wound round it from ten strands,
making 23,000 miles of jute yarn. Then comes the
outer coating formed of the ten covered iron wires. The
iron wire itself is 23,000 miles in length, and each wire is
covered separately with five strands of tarred hemp, 135,000
miles of the latter being required, making together an ag-
gregate length of material employed of 215,500 miles, or
very nearly as much as would put ten girdles round the
earth, or form a line that would stretch almost from the earth
to the moon 1
The machines at work at East Greenwich are expected,
when fully at work, to complete about 12 miles per day of
the allotted task, but in those 12 miles are wound and twisted
more than 1,000 miles of the hemp and jute strand, iron and
copper wires, and gutta percha coating. The machines
that aid in producing these 12 miles of composite rope are
each constructed upon the same principle. As many bob-
bins as there are strands to be wound or twisted are placed
in a revolving frame, and the wires or yarns from each bob-
bin, led up into a small aperture, are entwined with each
other into one twist around a central wire or core, as the case
may be. The machines for covering the separate wires are
small and the bobbins revolve with great rapidity, making
as many as '6OO revolutions per minute. The larger machines
in which the cable is completed are necessarily slower
in their movements, the revolutions varying from 25 to 50.
The rope. is formed by a machine working vertically, and
not horizontally,as is the smaller ones, On a circular stage,
some 12 feet in diameter, are placed 10 bobbins, much in
the same manner as the roundabouts at a village fair.
Each of these bobbins, although carried round upon the
stage, makes a revolution upon its own axis for every turn
of the roundabout. From each of these a thick strand, al-
ready prepared in other machines, passes upwards to meet
at a small opening at tho top of the ascending core, and the
10 cluster around it and twine upon its surface their iron
and hempen strands, and all go off in company to ono or
other of the great tanks prepared for their reception.
As we have already intimated, there is an abundant sup-
ply of electrical apparatus at the works, and carefully ad-
justed battery power, which is continually sending its mea-
sured force along the wires, so as to detect the slightest
flaw or defect in insulation, and register with unerring ac-
curacy its extent, whether it be due to material or work.
manship, with a facility nothing but this invisible and,in-
scrutable agency can discover.—Aatlway 11rews.: