The Sun.
London, England, 1860-04-09 00:00:00

thickest cables, made by Glass and Elliot,' between
this country and Holland. By starting from Ire-
land, on the contrary, two or three miles from
shore at once puts the cable into from ::00 to 500
fathoms of water, a depth at which it would be
most difficult to find any wire whatever, no matter
what its size. There must always b scare risk of
its being found by an enemy keepin close in shore.
Naturally the best plan, therefore, is to submerge it
along that route where its chances of discovery arc
the least. In short, there is no valid .reason why
the Gable should be landed at Falmouth in prefe-
rence to any other place, while, on the other hand,
the reasons for its being brought to Ireland are so
strong as to make it almost a necessary measure of
precaution.
Before the form, weight, strength, and outer
covering of each portion of the cable were resolved
on, the Board of Trade took the utmost pains, by
consulting our chief electricians, to ascertain the
kinds best suited for the purpose and for long en-
durance under water. Researches into these mat-
ters have led to the adoption of a cable of dif-
ferent thicknesses, weights, and strengths, ac-
cording to the depths of the water under which
it will be laid increases—the whole forming one
continued submarine rope, which, if not perfect in
its mechanical arrangement, is nevertheless one
which holds out high prospects of ultimate suc-
cess. The core or conductor is,-of course, of the
same thickness and formation throughout from end
to end, being formed of seven No. 18 copper wires,
in all about one-eighth of an inch diameter—the
thickest conductor that has ever yet been made. The
copper strands of this, in accordance with the ad-
vice of the electricians, have been very carefully
selected and tested for conducting power, as even
the purest copper wire, from some unknown cause,
has been found to vary in electrical conducting
power as much as 40 per cent. Its power of con-
ducting heat also diminishes or increases in the
same proportion with its electrical sensitiveness.
Yet, though the conductor with its insulating
medium of gutta-percha is alike in diameter
throughout, the manner in which this core is pro-
tected, or we had better say the thickness to which
the outer covering is laid on, differs considerably.
Thus each of the two shore ends is made to rest iu
from 100 to 200 fathoms, and these for 30 knots
each way are very massive, at the rate in weight
of seven tons to the mile. The next length at each
end is also of 30 knots, and will rest in from 200 to
400 fathoms water, and is far this depth a very
massive cable, weighing about five tons to the mile.
By the substitution of a finer gauge of wire at each
two or three miles or so, this gradually tapers down
to meet the first deep sea length, which will be laid
in from 500 to 800, or, possibly, even 1,000 fathoms,
The length of this portion of the cable is 940 nau-
tical miles, its weight in air two tons per mile, in
water about 34 cwt. The deepest deep-sea portion
across the centre of the Bay of Biscay extends over
about 280 knots, though 360 knots are being manu-
factured to meet contingencies in submerging.
Here the depth averages about 2,500 fathoms,
equal to the very deepest parts of the cable plateau
of the North Atlantic. To overcome the difficulties
of this vast depth of water the cable is strengthened
by the introduction of steel wire in its outer cover-
ing, and reduced to weigh in air only 26 cwt.,
in water as low as 13. The weight of the Atlantic
cable in air was one ton, and in water about 15 or
16 cwt., per mile.
The different weights of the different parts of the
cable are, of course, entirely due to the thickness of
the outer spiral wires with which it is covered.
. The conductor, with its threefold insulation of gutta
percha and Chatterton's patent—which latter, by
the way, is not equal to an additional fold of gutta
percha—is all served round alike with yarns of
tarred hemp closely bound in, and over which come
the outer wires of various gauges, No. 1 gauge, the
thickest known, being as thick as a cedar pencil,
and so on up tr No. 45 gauge, as fine as cotton. The
two heaviest shore ends, then, of 30 miles each, are
covered with 12 No. 3 gauge wires, which brings
its weight up to seven tons a-mile, and its breaking
strain from 25 to 30 tons. The second land ends
are enclosed in 12 No. 5 gauge wires, of five tons to
the mile, and equal to about 15 tons' strain.
The first deep-sea length of 950 miles for from
500 to 800 fathoms is closely covered, like the At-
lantic, with 18 No. 11 gauge solid iron wires, weigh-
ing two tons the mile in air, 33 cwt. in water, and
equal to a strain of nearly eight tons. The deepest
sea part is enclosed in 12 steel wires of No. 14 gauge,
each wire being spun round and enclosed in a sepa-
rate strand of hemp, in order, if possible, to take off
that dangerous springiness and tendency to kink,
which makes all steel wire rope, even when coiled
so lively, and so much resembling a cargo of live
eels. The cable, the chief points of which we have
thus described, is necessarily a most expensive one,
for, as we have already stated, the Government have
contracted that all parts of the material and work-
manship are to be of the finest possible kind.
Nevertheless, in spite of all the care that has
been taken to secure a good rope, and the improve-
ment which, with regard to strength with a certain
amount of lightness, the deep-sea portion of this
cable undoubtedly displays, it is still, we are sorry
to say, constructed on the old self-destructive prin-
ciple of spiral iron wires round a soft core—one of
the most faulty mechanical arrangements that could
have been attempted. There is not a single en-
gineer of eminence who does not condemn the prin-
ciple of laying on the outside wires spirally, in-
stead of longitudinally, in a line with the strain
they have to resist. 'Why the old arrangement
is persisted in at the present day it is difficult,
to imagine, unless it is due to the fact that most of
the wire-rope manufacturers have their machines
constructed for laying on the wires spirally, and
do not care to make others which will render the
completion of their work slower, more difficult, and
less profitable. Four years ago, when the plan of
construction of the Atlantic cable was resolved on,
we most strongly deprecated this arrangement,
and the event has so clearly justified what we then
pointed out would be the consequences, that we
may be excused for quoting the opinion on the
present occasion
"Whenever a cable is constructed with spiral
wires round a soft core any severe strain in paying
it out must, by stretching the outside wires, either
attenu ate or break the insulation. of the copper con-
ductor. This is a simple fact, which those least
conversant with mechanics can easily understand.
We do not mean to say that the Atlantic cable
cannot succeed, but the chances are very much
against it, and it is certain that before it has been
down 12 months it will, like most others similarly
constructed, be perfectly useless. If it does answer
even temporal ily, it will not be due to the plan on
which it is made, but in spite of it."
We shall on another occasion inform our readers
of the chief principles on which the light cable
before mentioned is being constructed, and the
prospects which cables of that description hold out
of being successful when laid. All that we have
at present to add with regard to the Gibraltar
cable is that the contractors undertake to sub-
merge it at their own risk and expense; and, to
insure proper fulfilment of this portion of their
task, the Government very wisely retain 5 per
cent. of the price of the whole cable (which is
in all nearly £300,000) in their own hands, and
further compel Messrs. Glass and Elliot to give
security to the amount of £20,000 that the rope
shall be successfully laid. It is proposed to sub-
merge it in two equal portions—one from Gibraltar
to Cape Finisterre, and one from Finisterre to (we
hope) the southwest coast of Ireland. It is antici-
pated that the whole rope will be ready for laying
about the middle of September next.—Times.

M. Paulin has been appointed professor of singing
at the Conservatoire, in place of M. Faure, resigned.

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