The Madisonian. [volume] (Washington City [i.e. Washington, D.C.]) 1837-1845, 1840-11-13
ELECTRIC TELEGRAPHS AND PNEU-
MATIC TUNNELS.

The investigation is of so interesting a nature,
and the application Of electricity to the convey
ance Of intelligence may ultimately be of such
vast importance, that we shall make no apology
for here appropriating the whole of an article on
the subject from late number Of the Inventors
Advocate:
"The observation of the effect of current Of
electricity in DETECTING magnetic needle, was
the first step in the progress Of discovery in the
science electromagnetic; the application of
this peculiar action has also been the first sue
cessful step towards bringing the principles Of
that science into practical use. Professor
Wheatstone and Mr.. Cooke have devoted much
time and attention in bringing the electro-mag
netic telegraph into operation; and it was under
their management that the telegraph on the
Great Western Railway was laid down. To
those who are unacquainted with the nature of
electromagnetic action, il may be interesting to
know the means by which instantaneous com
munication between remote places can be made.
The details OF the arrangement may be varied
and simplifed, but the principal action is the
point Of most interest. 1t was discovered by
Professor Orsted, that when the wire, which
unites the two poles of galvanic battery, is pla
ced over a magnetic needle, in the line of the
magnetic meridian, that end OF the needle which
points towards the negative pole Of the battery is
detected towards the west. When the wire is
placed in other positions, the DETECTION varies;
but in all cases the movements of the needle
show that it is strongly influenced by the electric
current when il passes near to it. The extent Of
the DETECTION depends upon the strength of the
electric current, and the sensibility of the needle;
but it can, in no case, exceed ninety degrees.
Let us suppose, then, that we have number of
magnetic needles, with wires passing over them,
each one which may be, at pleasure, connected
with galvanic battery, so as to cause current
of electricity to pass over any needle which is
required to be moved. We should thus have
all the elements ofan electromagnetic telegraph.
For instance, the movement of each separately,
or in combination with others, may be symbol
cal Of understood meanings, and as the current
of electricity passes through insulated wires, TO
distance without any known limits, at the rate
Of 100000 miles in second, these symbocal
communications might be kept up from one end
of the kingdom to the other, instantaneously.
The electromagnetic telegraph on the Great
Western Railway consists OF five working mag
netic needles, acted upon by five wires, which
are insulated from one another by being wrapped
round with cotton and lndia-rubber varnsh.
These needles are fixed to dial-plate, on which
are twenty letters of the alphabet, and the dial
plate is so arranged, that, by the movement of
two of the needles, any one of these letters is
pointed to.
The communication, therefore, may be intelli-
gibe to any one, and may be read off as the let
tiers are Indicated In order to increase the ef-
feet of the electrical current on the needles, the
wires connected with the battery are coied
round near the needles, which greatly adds TO
the power of the electricity in DETECTING them
from the magnetic meridian contrivance
has also been made for giving signal at each
station, so that the person in attendance may
know when any communication is about TO be
made. This is effected by directing the cleo
trio current through coil Of wire twisted round
a piece Of soft iron. The iron then instantly
becomes powerfully magnetic, and draws out
the iron detent bolt Of an alarum, which direct
" commences ringing. The mode of commu-
nication between the wires and the battery, and
breaking il again, is easily managed by keys
like those of piano forte, so that the telegraph,
after little practice, may be worked with great
rapidity. The distance to which the present
telegraph extends is thirteen miles, but profess
sor Wheatstone stated, in his evidence before
the committee, that from the experience he has
had of the working Of that telegraph, there is
no reason TO suppose the communication might
not be extended with the same success all the
way to Bristol. A person touching the keys Of
the telegraph in London, would thus be able in
stantly to communicate with the person at the
station In Bristol either by night or day. The
cost OF the telegraph TO Drayton was 200i. per
mile, but that was the first experiment and con-
sequently would be attended with much greater