, 1875-04-24
SOME REMARKS ON THE ELECTRIC
TELEGRAPH.

The fact Of this island being put TITO %elsotri-
cal communication with other parts of the
world naturally causes attention to be drawn
to the subject of telegraphy generally, so at
the risk o. W. AIRY ing The IT aders of the Avis we
shall again draw attention to srme Of The details
of the subject. 1t is we'll known that the cleo
trio telegraph is not really The invention of any
one man. Whtn in 1897 Cooke and Wheat>tons
brought out the needle telegraph they simply
applied the discoveries Of a number OF different
men, extending over 3 considerable interval Of
time. Let US take FIRST the battery. The source
Of electric power. 1t originated in VOlta'S
experiments on the production Of electricity
in frogs legs, and altogether apart from any
idea Of communicating TO a distance, but the
sequel of his experiments was the battery,
substantially the same as that now In use 10
many places, and not differing essentially from
any of The many known forms of it. Volta's
copper hook on the iron railing with the fluids
Of the frogs leg, that is to say, two different
metals in a liquid, soon became a plate of rop.
pei and one Of zinc in a jar Of weak SulphuriO
acid, and this, with certain notifications and
additions, is still largely in use. Our own tele.
graph cables are being worked with this kind
OF battery. But the battery though play
ing an important part in telegraphy, as
afordiDg a ready means Of q supply Of cleo
tricity does not play the most important
one; a current Of electricity can be pro.
duced 10 a variety Of ways, the rapid rotation
of a magnet in proximity TO a wire beinr ano.
ther of The bts 81 kF0Wn. We may also Instance
Armstrong; machine, where electricity il pro.
dused hy the friclitn of a jet Of ste am rushing
cut from a boiler through small holes, and the
hermO-electric pile, where a series of bars Of
hismuih and %antimOny alternately, or any pair
OF different metals, are sOldtrtd to ore another
and every other junction being heated, a eur.
rent OF electricity is produced.
But now having a supply Of electricity, va
wish TO know hrw to convey it 10 a distance.
and here something much older than Volta's ex-
PerlmeniscCmesln AT an early Stage in the his
tory of electrical science substances were divided
into ~electricS and non. ~electrics, such substances
as glass, which were found TO be electrified
after being rubbed, heing called %electrics. others.
az metal, where no trace Of electricity could he
found under similar conditions, being called
non. %electrics. 1t is remarkable We use cnly
The so-cslled non-electrics to carry our current
to a distance, further researt hes shelving that
it was not that they could not be electrified.
Out SIMPLY that the electricity ran along them
ana escaped as fast as generated !: thus the
land telegraph lines consist of iron wire and
the part OF a submarine cable which transmits
the message of copper. But The so.called
eiecirics or as We now call them insulators
also play their part in C~on6nipg The elect
10 Its metallic path; if We ran our wires simply
along the ground or across the water without
any covering, a very small part of the current
would be received even at a short distance:
the large part would find paths Though the
eartn or water and be lost, but We can con.
fine it by surrounding the wire with some
insulator of wlich the very be>t 10 cir DRY
air which is transparent to heat and light and
which conducts even sound very we'll 10 almost
impervious to the passage of electricity it
10 only when some great electric force, such