The Washington union. [volume] (City of Washington [D.C.]) 1857-1859, 1859-03-16
IMPROVED ELECTRICIL CABLE

On the evening of the 22d the Rev. Walter Mitchell,
NJ. A, delivered a lecture con the Atlantic telegraph,
and electric telegraph in general, = at the Russell Institu-
ton, London. The most novel feature of the lecture,
and one which ELECTED great interest, was the description
of some very interesting experiments 10y Prot. Hughes,
the inventor of the printing telegraph. These expert
ments have not only cXenplited the defects of the pres
ent Atlantic cable, and the cause Of the interruption Of
electric communication, but also afforded a demonstration
of an easy method of preventing such accidents for the
future. A copper wire insulated in the ordinary manner
was placed in u bath Of salt and water. An electrical
circuit was made, interrupted only by the water. The
complete insulation of the copper wire was indicated by
the needle Of one of Mr.. Henley's most delicate galvau-
ometers connected with the interrupted current standing
at zero. A hole of considerable size was then made
through the gutta percha, allowing the salt water to
reach the wire. The electrical circuit was then imme-
diately completed by the water, the detection Of the
needle, and its permanent position at 900, marking what
is technically called 'dead earth, y OF, in other words,
the complete escape Of the electric force through the
opening into the surrounding water. A more minute
hole was then made, when the following curious phe-
nomena presented themselves: The needle of the gal
vanometer was detected about 700 but, instead of &c.
naming stationary at that point, kept vibrating irrcgu-
larly through arcs of two or three degrees ON each side of
100. The porplexing vibrations of the galvanometers
applied TO the electric cable Were thus exemplifed. It
become, therefore, exceedingly probable that the vibri-
lions supposed 10 be produced by earth currents arc moth
ing more than an indication of the minute nature of the
flaw in the gutta percha, which has destroyed the con
Quoting power of the present cable. To remedy such de-
fects for the future, Mr.. Hughes has devised q form Of
cable as simple us it seems TO DO efectual in performing
its work.
Gutta percha is more or less porous. Minute flaws may
exist which may not show themselves until some time
after the immersion of a cable. This was exemplifed by
Mr.. Henley, who discovered a flaw in his Tasmanian ca
BILE, which did not show itself until ii had been three or
four days under water. To meet these defects, to fill up
any pores in the gutta percha, and also to cure any acct
dental fracture or puncture Of 1t, Professor Hughes intro
duces a viscid semi-fuid substance Of non conducting
character between the conducting wire and the quit
percha. The gutta percha covering Of the wire is drawn
out into q tube q little larger in bore than the wire. the
space between them being filled with the viscid fluid. As
soon 81 any punciure is made through the gutta percha
covering NE fluid oozos out, and Is Of that nature that il
hariens as soon rs it comes in contact with the surround
ing water, a puDcture was made in a piece of this pre-.
pared cable while in the bath. The needle of the palya-
mometer instantly registered dead earth, showing the in.
jury received by the cable. But immediately the fluid
began TO ooze out and repair the injury. In about half
a minute the return Of the needle to zero indicated the
complete restoration of the covering of the cable. Not
only was this demonstrated by punotures, but long sits.
two or three inches In length, were speedily filled ND.
This imitation of the process by which natire repairs in
juries done to trees by the flow of the sap and IL coagula-
ton opens out a good prospect OF overcoming the defects
which have lately manifested themselves in several deep
sea telegraph cables. 1t was stated that there were no
mechanical difficulties in the way Of the manufacture of
such a cable, and that il would not be more expensive
than those now made.
"he lecture was also illustrated by some Of Mr.. Hen
'"l'cats relay Instruments. which
ley's very perfect ana ,.,..--
excited deserved admiration.