The daily dispatch. [volume] (Richmond [Va.]) 1850-1884, 1882-11-08
r.-.,none possibilities.

fIE TffE TELEfIuNE siHiEho VIZ" -"
spEcr TO LoS0 DISTANCES.
The difficulty Of conycrslng over long
distances by means OF the telephone, when
l. not an insupcrablc one, even NJ tne pre-
sent stage OF development OF the mstru-
ment, arises from the peculiar surround
| ings Of the lines In actual use. In PERSIA
Speaking has been done between IaDreez
and Tifls, 800 miles apart; In Austraiia
over 800 miles; In America oven 4io miles,
In India over 800 miles. In all these cases,
however, IL was done either ut night
or under exceptional circumstances,
and the wires were overground'
Could we construct line between
Baltimore and Cincinnati on poles.
lofty, separate, and distant from oil
other wires, there would be no difficulty in
conyersng between the two cities. IL
would be different IL the line were under
ground or submarine. Speech has been
had through the submarine wires con-
Meeting Dover and CALAIS, Dartmouth and
Guernsey. and Holyhead and Dublin, but
there il no case on record, il Is believed,
whore conversation has been held through
more than one hundred miles Of marine
cable. The minute quantity Of electricity
employed for telephone messages Is lost III
any great length of submarine wire. \
cable must be charged with electricity from
end TO end. and il it has impaired to it
charge insufficient for this purpose, no sig
nal appears at the receiving end. Mr.. W.
II. Preece, +. II. s., quoted in the Scieihi-
fc American, is authority for the statement
that the newspaper report OF the hearing OF
the Commandment Of Alexandria at Malta
Is not correct. s'ln the first place." he
saws, .'thc experiment was not tried, and
even if il had been tried, 1t could not have
succeeded" According to the same cleo
trician. twenty miles is the limit OF dis
lance over which, with our present appa-
ratus and present knowledge, we can readi-
! ly speak. The neighborhoOd Of other wires
| is, has been already intimated, prejudcial.
When two or more telephOne-wires run
parallel the message travcrSing one can be
heard on the rest The vicinity OF tclc-
graph-wire is still worse. Every cur
rent on the telcgraph-wire is re-
peated in the telephone, producing pecu-
| iaIly irritating Kissing, bubbling, fry
ing sound that browns speech. This effect,
due to induction, or leakage, is sometimes
pleasant or dverting, rs when music, pass
ing on one telephone wire, Is heard on all
! the others, and conversations meant for
loving ears reach unsympathetic listeners.
The worst enemy the telephone wire has,
| however, is the elcctric-ight cable. The
powerful alternative and intermittent cur
rents used in certain systems OF lighting
are death to telephones, producing an in
cessant roar that renders speech impossible.
| Various devices have been employed to
cure these interfercnceS. The only eflcc-
tive one is to use complete metallic cir
cult, the two wires OF which are very close
togethcr-twisted, in fact, the one around
the other, so as TO maintain mean
average distance between themselves
and the disturbing wires. Whatever be the
strength OF the influence Of the disturbing
cause on the current IN one OF the telephone
wires, il is the same upon the other and in
an opposite direction, so that its power OF
interference is reduced to zero. This plan
was the invention OF Mr.. BroOkeS, Phla-
dclphian, and has been adopted with per-
feet success by the English pOst-oilice. II
costs, OF course, more than the slnglc-Wirc
system, but its absolute freedom from
overhearng, its privacy and the absence Of
cracking, make it worth the extra
cost. lis success, whether underground
or overgrOund, in the streets Of cities
makes it the system OF the future.
Submarine wires are invariably made with
twist, so that they do not suffer the
interference with which single lines are
troubled. Manchester. England, has over
AGO miles OF ovcrgrOund double wire
twisted on this plan working thoroughly,
and there, in the midst Of the mulutudcs
OF busiy-occupied wires Of a great city.
conversation can ejheld over distance
OF 76 miles. Mr.. Irecce prOnOunccS the
venerable theory that the earth is great
reservoir OF electricity, from which either
positive or negative electricity could he
extracted at will, exploded. Currents are
traversing it. The return current of tee-
graph lines, one wire OF which is ground
ed, can be picked up rs it trayerSes the
soil. Telephones placed in the attic OF a
building, and connected on the one hand
with the gas-pipcS and on the other
with a wire coming up from the
ground floor, have been found to
steal the messages sent from telc-
sraph-otlice, 80 yards away. Several cases
arc known where telephones have picked
up messages from teIcgraph-lneS miles
away. II is. therefore, desirable that the
earth should not enter the telephone cir
cult. When electric-light wires are
grounded this is seen TO be not only Gcsir
bic but essential, and in case OF a thunder
storm the cXpcdiency Of cutting the earth
out Is shown to be Of the highest order
Every flash Of lightning, no matter how
far off, is indicated when the earth forms
part Of the telephone circuit. There are
"oarth currents" which are at times 50
strong that when taken up by the telephone
they make noise "aS il your brains were
boiling." These are, however, so weak,
ordinarily, that the tclcphonist has little to
fear from baltimore San.