The Sun.
London, England, 1863-08-12 00:00:00

THE TELI IGRAPH TO INDIA.

If mechanical app, .
'aances are to be depended upon,
and if the most caret
al and experienced supervision
of all relating to the
scientific perfection of a sub-
r avail, the whole of England
marine cable is of an:
before next 'Alarch w ill have at command a. means
of daily, if not hourly. , communication with Madras,
Calcutta, and Bombe: r- The activity of grey shirt-
in gs or the dullness of mule twist ought to be known
here to the fraction of ;an anna every morning; and
the news from China a tnd Australia anticipated by I
exactly the difference c f time between an overland
passage and an overlent I telegraph, which means the
difference between 30 d ays and five hours. So care-
fully have the plans be en matured, so quietly has
the cable itself been :manufactured, the: the an-
nouncement that the (expedition will in a few days
begin to leave these eh nes to accomplish such great
results comes upon us win a suddenness that is almost
startling, and the noti,3n of being in instantaneous
communication with all India soon after Christmas
seems almost too good and too astounding to be ca-
pable of such immediate realisation. Such, how-
ever, is at least the object with which the expedi-
tion will start, and such, we have not the slightest
doubt is the object which it will accomplish with
triumphant success. The Indiin Government in
making their cable have proceeded so quietly that,
except to a few electricians and scientific men, the
announcement that a cable to connect this country
with Calcutta is nearly made will, we fancy, be
quite a surprise to our readers.
The political necessity which renders it essential
for her Majesty's Government to be in frequent
communication with the great Indian Empire it is
needless here to describe. The Government of such '
distant possessions as India and Australia can
scarcely be carried on in the bureaus of Downing-
street without some readier means of conveying
instructions than that afforded by the Post. Minis-
ters have long been conscious of this fact, and the
failure of the attempt to establish electric commu-
nication with India via the Red Sea must be fresh
in the memory of all. Profiting by the bitter expe-
riences of that unfortunate undertaking, the Govern-
ment have wisely determined to take the construc-
tion and completion of the present line to India into
their own hands. The India Board have placed the
general superintendence and control of the line
under Lieut.-Col. Patrick Stewart, R.E., au officer
as well known for his gallantry during the Indian
mutiny as for the great services he rendered the
Government by the construction and maintenance
of the telegraph lines through the wildest districts
of Central and East India. For the immediate elec-
trical and engineering superintendence of the line,
and also for the arduous task of submerging it, the'
Indian Government have selected Sir Chas. Bright
and Mr. Latimer Clarke, and under such auspices
and supervision its manufacture is now approach-
ing completion at Mr. Henley's telegraph works,
North Woolwich. Whatever may be its ultimate
fate, it was quite certain that there never yet has
been a cable manufactured with such care, or one
which, in point of " conductivity" and insulation,
comes so nearly up to the standard of absolute elec-
trical perfection. The design and construction of the
cable differ very materially from any line hitherto
laid. Every operation in submarine telegraphy—
even the great Atlantic line has contributed its
quota of valuable experience; for, though success-
fully laid by Sir C. Bright and his assistant en-
gineers, in spite of the imperfect construction,
it was destroyed by the injudicious electrical
treatment it received after submersion. This
fact is now so well established that the cause of
the failure of the Atlantic cable may bo consi-
dered es set at rest for ever. The insulation of that
line was not very perfect, as may be imagined from
the infancy of the science at that time, but yet the
electrical power used was such as would infallibly
break down even the most perfect cables manufac-
tured at the present day. Of this our readers may
judge when it is stated that the large induction coils
first used in signalling between England and
America were probably equal in electrical power to
3,000 battery cells, while now it is found inexpedi-
ent to use more than two or three cells in 'working '
the longest submarine lines in existence, Some of
this great power was no doubt used in the vain hope
of forcing signals through the line at a greater speed
than the very slow and unremenerative rate at
which it has alone been found possible to communi-
cate through an unbroken length of 3,000 miles.
The result was disastrous, but the experience, though
dearly bought, has proved of great value. It has
taught electricians the value of moderating the
power used in working lines, and above all has
pointed out the imperative necessity of having no
single section of a submarine line of more than 600
miles in length. To lay long submarine cables in a
continuous length without intermediate stations has
been found to answer no other purpose than that of
greatly diminishing the speed of working and multi•
plying every imaginable risk both of manufacture
and submersion. The Indian Government, acting
under the judicious counsel of their ecientific ad-
visers, have wisely determined to divide the Persian
Gulf cable into three sections, though its total
length will not exceed 1,500 statute miles.
The faults which led to the destruction of the Red
Sea line were of another character. Though it was
manufactured and tested with a care greatly
superior to that taken with the Atlantic cable, it
was submerged in a way which rendered its
ceaeing to work a question of a few weeks more or
less. Sheathed in a covering of small wires, quite
unprotected from corrosion, it was laid without any
allowance for "slack" cable to fall into the irregu-
larity of the bottom of the sea. It consequently
lay strained across the points of the inequalities,
with a tension of several thousand pounds. As the
unprotected wires rusted away, and the suspended
portions of the line became loaded with coral and
barnacles, the whole line crumbled into hundreds
of pieces by its own weight. This is no mere hypo-
thetical opinion, but a fact, which was amply proved
by the expedition to the Red Sea in 1561, under
Mr. Latimer Clark. There can be little doubt that
the same cause led to the temporary failure of the
Malta and Alexandria line, as well as that laid for
the French Government between Toulon and Algiers.

To obviate this cause of danger, which in the
above-mentioned lines has probably occasioned a loss
°T property to the value of over a million sterling
the Persian Gulf line is cased in :2 No. 7 gauge
'irawn iron wires, thickly galvanised, so as
to effectuallythere more
to prevent their corrosion. But, in order
of iinetaore effectually the permanent stability
with two litho whole finished cable is thickly coated
with two coe4t..",ings of tarred hemp yarn, overlaid
by Sir enati":ll,3 of a patent composition invented
composition
tar,
and Mr. Latimer Clark. The
Stockholm etatii of mineral pitch or asphalt,
tarn proportions, Powdered silica, mixed in cer- ,
While yet warm it laid on in a melted state
lers, which give it Z 48,1 ed between circular rol-
quite cold this form, llza4, smooth surface. When
covering of great
strength and. :perfect Zitrl"
to water, and incapable
of btef, totally impervious
4 destroyed by the
minute animalcula which existni
their attacks, the cable
warm latitudes, and which,livail°llabundance in
is not protected against
ease
every atom of the hemp, as iattacks, eat
of the cable laid between Toulon Ilan:4
Galvanising the wire is in itself an almostkigirs
p,rieet
protection from rust—certainly for many year
the good condition of the cable picked on oPth"
Kooria "%lonia Llancl3, a part of which was gaivela.
showed, as far es the galvanising was con.
cerned. But, with the final protection bath foam
rust and animalculz which Bright and Clark's cam.
pound affords, there appears to be no reason why
this cable, when once laid in shallow or deep waters,
should not remain for 100 years to come. The
copper conducting wire is composed of four segments,
drawn into a hollow tuba in such a manner as to
appear like a solid wire. By this means all the ad-
vantages of a strand wire ere combined with the
condensed bulk and small surface of a solid one.
The copper from which the Wire is drawn is espe-
cially selected by the engineers for its high capacity.
for conducting electricity. It is, perhaps, :iot gene-
rally known that different samples of copper vary
as much as 50 or 60 per cent. in this respect,—that
is, some specizness of copper-wire will conduct elec-
tricity with greater facility than other specimens
double the thickness, though physically there may