Green-Mountain freeman. [volume] (Montpelier, Vt.) 1844-1884, 1869-08-25
How the telegraph is Worked.

The following very interesting 1Jte5 en-
the working Of the telegraph are taken
from a recent lecture on Modern Engi
neering' by William J. MeAIpine, c. L.,
who Is one Of cur foremost authorities in
this country OF engineering topics, and we
feel perfectly confident that We have here
some able enciucers-Presiden White, of
the Cornell University, - the contrary
Notwithstanding.
Telegraphy may, with propriety, be
considered one Of the branches Of engineer
ing. and IS peculiarly of modern develop
ment \ clever writer SAYS that it may
be read by each Of the five senses. On
land lines each signal IS made by suspend
ing the flow of the electric current for two
different intervals OF time, called dots
and dashes-the use Of which, in different
orders, constitutes the alphabet Of the
telegraph When these are printed, they
are read by sight but ordinarily the
operator reads them by sound, as easily
as a musician reads the letters OF the scale
by the same sense. If the operator has
no instrument. he will grasp the wire in
his hand and read the signals by feeling
the intermjssions Of the flow of the electric
current In ike manner, by placing the
wire across his tongue he can taste the
same intermi-sion but this Is a dangerous
experiment And II ia said that the clec-
tricitv can be made to decomp0se certain
chemical solutions and thus produce
puneent odor in the telcgraphic alphabet,
which can he read by smelling but for
this DO not vouch | believe that the
method Of signaling through the Atlantic
cable Is known in detail to bat few per
sons. The operation j. exactly reversed
from that OF the land wires.
The gutta-percha covering of the
copper wires, under the pressure Of
of the electricity which Is being sent
through them TO the extent Of ninety per
cent The first portion OF the electric
wave OF ten per cent. crosses the ocean
G7O0 niles in two seconds, and it would
be followed 10y a succession Of waves from
the restoration of that portion of the
electricity which has been absorbed by the
gutta-rcrcha in impulses, and the signal
would be repeated ike echoes. and pro-
duce not only confusion, but great delay.
To remedy this, Professor Narley introdu-
ced a KEY, which sends alternate currents
positive and negative, at such intervals aS
allow the first wave of ten per cent TO
pass forward and then that portion alb
sorbed by the covering l. ncutralized 10y
its opposite. and the cable Is cleared for
the transmission of a second pair of cur
rents. The battery used Is a very small
one, three Of Dauiells cups,) and the
signal, being ten per cent of this small cur
rent, Is poTerless to move any OF the other
instruments in use ON land. The instru-
ment used consists of a minute poarized
needle, suspended on single strand of
SPIDERS web, OF one from the silkworm.
In the middle of this minute needle is pla-
ced an almost microscopic mirror, which
reflects a slender ray of light from a pow
erful lamp.
The currents Of electricity affect this
needle alternately to the right and left for
a space of time corresponding TO that occu-
pied in the signal Of the land line, the same
kind of alphabet being used in both eases.
The receiver mot OPERATOR sits in dark
room and the small mirror reflects the ray
of light upon piece of white paper before
him, on which a black line Is drawn, to the
right and left Of which the light is alter
nately reflected. The receiver reads these
signals 10y sight and transmits them to
another person, placed outside Of the dark
room, by means OF an ordinary Instrument.
\ short time since, General Reynolds told
me that he had sent message, without
either wire or cable, ninety-two miles,
across an arm of Lake Superior, by means
of the heliotrope, or mirror, and on the
return of his messenger, who had been sent
with written copy, he found out that the
heliotrope message had been received, un-
derstood, and obeyed.
. He had two assistants, who had been
telegraphic operators, who had for a whole
summer been amusing themselves in talk
ing to each other with these instruments,
though they were stationed ten, twenty, or
thirty miles apart When the rebel Cen
eral Morgan made his great raid through
Indiana and Ohio, he captured one of my
operators, and compelled him to telegraph
in General Lew Wallace's name, to Gin
cinnati, asking how many regular troops
were in that city. Morgan read by
sound, and therefore the operator did
not dare to intimate that he was under
duress, and could only venture to add an
extra initial to its own signatures. The
receiving operator at Cincinnati knew that
Morgan was in that neighbOrhood, and sus-
pecting from the extra initial letter that all
was not right, replied greatly exaggerating
the force of regulars, and the consequence
was, that Morgan changed his route to
circuit of twenty miles beyond the city,
and thus saved it from sack, and the
probable loss of millions of dollars"