The daily exchange. [volume] (Baltimore, Md.) 1858-1861, 1858-10-14
THE ATLANTIC TELEGRAPH.


THE ATLANTIC TELEGRAPH.
Cor. Of the London Times
VALENTIA, Friday, Sept. 2i.-Since my last COM
munication no Improvement has taken place in the
electrical condition of the Atlantic cable nor in
deed until within the last few days have any opera
tions or experiments beyond those the results of
which have already been communicated been nm
dertaken to ascertain the nature of the leakage in
the cable, the possibility of working tbrou0b IL
IN Its present condition. Up toyesterday every
thing remained in statu quo. During each alternate
h0ur the regular succession of sigpas previously
alluded to are despatched, and during the intervals
the galvanometers of Professor Thomson are
watched for some indications of currents from the
other side; but these, unfortunately are seldom
seen at ALL and still rarely can these slioht de-
Elections be depended on as currents from New
foundland However, there is still this much cause
for satisfaction, that the fault does not pet worse a
any time, while it occasionally for time improves
considerable and distinct ''reversals" from New
ioundland being discernable
The opinion prevalent among many here that the
principal fault in the cable is comnarativeIv near
Snore daily gains ground and, though Professor
lhomson's opinion is directly opposed to such a
suppositlon, l cannot help thinking that there
really is more in it than was at first sunnosod -
For the reasons given in nv last letter there il No
d0uot, fault existing in the cable upon the bank
winch divides the shore water from the depths of
the Atlantic, about $50 miles from the Irish coast
but this fault without the existence OF several mi
nor faults nearer shore would not account for tbe
total interruption of the currents sent from either
termini. All that Prof. Thomson, Mr. Henley or
Mr.. 'arley can say respecting the fault is that it
gives resistance to the electric current canal to
800 miles of the cable. But it does not therefore
follow that the interruption is 800 miles away; for
by passing the current through few yards of fine
wfe or basin OF salt water, the very same amount
Oh resistance can be produced. Though the distant
FAULT may tend to interrupt the small portion of the
electric current which passes the nearer faults vet
II these more accessible ones were repaired it is
Otr hO,o
matter that the supposed loss of insulation out at
sea would not materially affect the working of the
line. s.....
The more recent advces from Newfoundland de-
cldedly tend to strengthen the opinion that the main
interruption is close to this place. Mr. CYRUS Field
In writing from America, SAYS that 'sno messages
have been received from Ireland since the lst inst
though the insulation of the cable remains perfect
NOW, according to the experiments of Professor
Thomson and others, it has been ascertained that
loss OF insulation 800 miles from either shore would
anect the currents sent from both ends equally
whereas, II tae defect close to either shore the
loss OF insulation would only be apparent at the
terminus nearest to it. A very similar defect to
the present occurred short time ago in one of the
North Sea cables Mr.. Marley and other scientific
gentlemen tested the cable, and pronounced the
defect to be 10 miles off. The cable was accord
ngly under-run and cut at distance of 80 miles
from the shore, when it was found that the defect
was much nearer, and after variety of other
experiments had been tried the faulty place in the
tually in the portion of the cable buried in the
beach.
The above incident, which believe to be substan-
TALLY correct should teach the authorities of the
Atlantic Telegraph Company not to pronounce
their scheme failure until the theoretical exper-
Iments (Which are but uncertain guides no matter
how ably conducted) are verified in some measure
by practical tests. The practical tests cannot be
obtained without undermining and cutting the ca
bic for some distance from the coast. This opera
ton VIII undoubtedly require fine weather to rem
der 1t certainly successful. The usual season of
line weather. of which there has been very little this
year upon the coast, is now almost over, and peo-
pie down here already begin to lookout for the com
mencement of those violent storms which render
these parts of the Irish coast exciting if not anu
sing. places of residence during the winter time.
During October, which here as well as in other
parts OF the United Kingdom is usually fine month
much might be done towards undermining and
repairing at least some of the damaged portion of
the cable.
There is certainly no time to be lost, for every
week that the cable remains at the bottom dimln-
isles the chances of its being raised from the more
considerable depths should it be deemed necessary
to do so. The Cork steamer, which arrived here on
Monday last, brought Mr.. Henley's gigantic mag
net0-electric machines, which as soon as they were
landed were put together and got into operation
on the following day. The machines are a slight
modification of the magneto-electric machines
when in place OF batteries are used for working
over all the telegraph lines in Ireland, though, of
course, on gigantic scale, being the largest and
most powerful instrument of the kind yet construct
ed The two permanent magnets, from which the
electro induction is maintained, are each composed
OF ~ horseshoe steel magnets, two feet and Il half
long, and from four to five inches broad The in
duction coils attached to these each contain about
six miles of wire. Some idea of the power of this
instrument may be gathered from the fact that one
shock from it, if passed through the human body,
would be sufficient to destroy life.
ith the and OF this instrument Mr.. Henley hopes
to be able to work through the cable during some
part OF each day, even if the fault should prove If
reparable. The smaller instruments of the same
kind, which are used by the Magnetic Telegraph
Company, have been found to work better over
badly insulated lines than any other description OF
instrument What is undoubtedly true of faulty
overground lines may prove also of the Atlantic
cable; and certainly, as far as the experiments have
already gone, Mr.. Heney's instrument seems likely
to work through the line in its present condition il
anything will do it. variety of experiments have
been tried lately, both by Prof. Thomson and Mr..
Henley, to discover the relative power of different
electrical currents TO pass fault. For this pur-
pose the wire connected with the cable stripped
10 lts Sutta percha covering in one place and the
FAULT immersed in water.
The relative amount of electricity which passed
by the fault into the cable accurately measured
by delicate galvanometer 1t was found that n
current OF electricity direct from the battery cells
was hardly perceptibly reduced in quantity after
passing by break in the insulation an eighth of an
inch long, the induced current from Mr.. Henlys
magnet-electric machine was slightly INTERRUPTED
IN passing the fault, but the high tension in
duced coil currents which have been used from the
hrst IN sending messages from both sides of the
ocean, were found to be almost entirely stopped by
it. These experiments, besides showing the kind of
electricity best adapted for working through the
cable in its present defective state, also show most
conclusvely that defect in the insulation how
ever great, would not be sufficient to interrupt the
communication; SO that there must be several aultv
places in the line. That some if not the majority
of the places close to the land there can be very
little doubt
The soundngs from Vaentia for about 60 miles
to sea show rocky and irregular bottom which,
indeed, the PERCEPTIONS cliffs which line the coast
and the numerous lofty islands which surround it
in all directions, would show without the use of the
sea lead. Over these submarine hills and valleys
very strong current sweeps, to resist which it would
require cable at least three times thick as the
one now in The small piece of the Atlantic
cable which connects Valentia Island with the main
land distance of about an English mile, is repeat
eddy being cut and injured by the tide drifting it
across the rocky bottom, and it is quite possible
to suppose that the rapid current outwards from
the broad estuary of Dinge Bay may have the
same effect upon the thin Atlantic cable which runs
across its mouth. 1t is the unanimous opinion of
nearly all here that the laying of 10 or II miles of
the thick shore-end of the cable would tend perma-
nenty to obviate great many of the difficulties
with which the electrical department of this under
taking has been hitherto interrupted
Beyond the continuance of the few experiments
which have alluded to at the beginning of this
letter nothing will be done with the cable until the
preconcerted experiments at both termn ofthe line
have been made. They have fixed to take place
early in the closing month. The result of these
experiments will doubt show with great certain
ty the nature and position of the faults than could
be shown by experiments at one end only. These
researches will also demonstrate the possibility or
impossibity of making the line work in its present
defective condition.
TELEGRAPH SECRETS IN FRANCE.-It may be in
teresting to telegram transmitters in France to
Gated to Minister of the INTERIOR and that special
functionaries employed in selecting from the
various interesting dispatches messages of love, of
mourning, of business, or of despair, to the
leisure moments of the Government official. Hav-
ing had occasion of late to this beneficent gift
OF science somewhat extensively, | was curious to
observe that copies of each telegram taken be-
fore transmission. On inquiry, find that no less
than four transcripts are made for various depart
ments, and of course the ostensbe object is to put
Government in possession of possible or construc-
tive treason. But how is this end to be obtained
When Thompson sends word to ''look after his car
ba0 and transmit il nv the nnvt train - how il