Year: 1873

HOW tUt VOuutI ~ WI IhVus


The readers OF the Ledger doubtless
observed in the cable dispatches no.
tice that the cable laid in 1866 had
failed" at twenty minutes past twelve
o'clock on the day before and that an
electrician would leave London in the
evening to "locate the fault" They OF
course understood that it was the mis-
sion OF the gentleman mentioned to go
to the shore end of the cable on the
coast of Ireland, to ascertain Mt what
point of the two thousand miles OF cable
buried under tho sen the cable had been
injured or broken. And we have no
doubt some of them have wondered how
it was possible for the electrician to
know, or to learn, Vhere the fault or the
break could be. considering that some
portions of the wire were thousand
miles distant from his point of observa-
tion, and great deal Of it buried deep
from human sight two miles beneath
the surface Of the sea-. Yet every part
of that long distance, and every fathom
of ! / abyss of water, are within the
reach of the electricians instrumental
hands, and within the ken of his scien-
tifc eye. IL is quite practicable for
him to locate the fault v or the break,
within half mile of its actual position,
no matter where it be.


Although these far. reaching powers
are among the great marvels of modern
science, the means and the principles
through which they are exercised are
among the simplest things when seen
and understood. A telegraphic wire
will transmit an electromagnetic wave
or " current, in proportion to the square
of its diameter. The resistance to the
transmission of the wave diminishes in
proportion as the square OF the diane
ter is increased This is one law for the
electrician.


The second is that the resistance to
The transmission of the wave increases
in direct proportion to the length of the
wire or cable over which ii is sent
There two laws furnish the bases for
the electricians observations, calcula-
tions and results. He knows, to start
with, the precise amount OF resistance
that mile of the cable will oppose to
the transmission of given quantity OF
electro motive force. He has delicate
and wonderful instruments, made by
expert mechanics, that enable him to
measure this with accuracy for half q
mile or for ten thousand miles. Having
this knowledge and these measuring in
struments, and having control Of the
quantity of electricity he is putting on
the wire, he is able to calculate to a
nicely how many miles of. the cable it Is
transmitted over, before it encounters a
greater resistance than that which is
due to the length and diameter of the
cable Itself. At or near the end of that
number of miles of cable, though it be
a thousand niles from land, and two
miles under the surface OF the sea, the
'fault" or break the electrician is in
search of will be found.


Our readers should understand that
we are not stating any mere hypothesis.
This real wonder and seeming imposi-
billty has been accomplished again and
again. The principles through which
it is accomplished, are the discovery OF
one of those quiet, studious men, who
plod about in their laboratories and
workshops, and who are supposed by
many people to be wasting their lives
about things of little practical use, but
whose works, together with those of the
skilled mechanics, who cooperate with
them, really move the world along.


This particular student of the laws
of nature is Prof. Ohm, of Nuremburg,
Germany, one of several men whose
labors, like those of Oersted and our
American Prof. Henry, have made the
Magnetic Telegraph possibility The
delicate and wonderful instruments by
which those principles are applied, and
which enable the electrician to extend
his reach thousand miles oNt to
sea, and to the bottom of the ocean
abyss, have been at work in one of the
most modest work shops in this city for
several years. They are the tools OF
Philadelphia workman, who now leads
the world in the manufacture OF one
important adjunct in telegraphy-a
nearly perfect '.insulator. The simple
device for working the ocean cable is
there also.


This matter has been mentioned at
some length, for the benefit of the boys
and girls in our public schools, who
will see what grand and useful results
are accomplished by the application of
the simplest principles of science, and
that they may also understand that
they need but rarely go beyond their
own city to find whatever they may
wish to know, or to understand about
science, applied to the useful purposes
of ife.--Philadelphia Ledger.