Mineral Point tribune. (Mineral Point, Wis.) 1869-1938, 1879-06-25
PROGRESS IN APPLIED SCIENCE.
The Electric Light..The Bell Telephone
1.-The MiScroph0ne. Etc.
North American Review.

1.-The MiScrOphOne. Etc.
North American Review.
Electric incandescence, IS n source
of light. was first reduced to a practical
| shape about twenty years age by M. de
CLANCY in Paris, and by Mr.. Moses G..
Farmer in Salem, Mass. 10th of these
gentlemen seem to have developed
electric lamps operating by the incan-
descence Of a metallic wire and having
an efficient automatic regulator by
| which their constancy of action was Sc
cured; but the great cost D electricity,
produced at that time by the galvanic
battery, caused the abandonment of all
efforts to make any practical use Of
such apparatus. Now, however, that a
relatively cheap source of electricity is
found IN the magneto-electlc machine,
these old plans have been revived, and
we find in Mr.. Edisor's English patents
a redevelopment of the same thing.
They all operate on tie fact that
when a powerful current of electricity
traverses an insufficient conductor, as
a wire or narrow strip of Platinum, for
example, the same is intensely heated,
dIlt 81 pttitIitS ltttllitlolG. SpilS vi
wire, strips of platinum, or the like,
are therefore SO arranged that n cur
rent shall pass through them, and so
make them luminously hot or incan-
descent. As this incardescence is
greatest near the fusing-pont of these
substances and their fusion would
of course interrupt the action,
various ingenious ,~ontrivanceS
are adopted by which the current is
automatically shut off or diverted if it
approaches too near to tbs disastrous
result. Thus, for example, the strip of
incandescent metal itself so operates a
lever that as soon MS its expansion
reaches a certain degree it closes a cir
cult, which diverts part of the current
into another conductor.
There are a multitude of these con
%tricances, and almost every day sees
new ones added To the list, but so far
they have all been very elaborate, often
complicated, and, as a rule, expensive
instruments.
Another plan is to use, m place of n
metal which may be fused a thin rod
of carbon, which cannot be fused, and
whose tendency to burn is overcome by
%inclosing 1t in a glass vessel filled with
some gas when cannot combine with
1t, nitrogen for example. Lamps Of
this nature have been largely expert
mented with, and inventors are still
laboring upon them, but as yet the sue
cess obtained Is not such as to warrant
their practical introduction into actual
use.
In all plans OF obtaining light by cleo
trio incandescence so far put shed, the
cost of the light has been many times
greater than with an electric arc.
On the other hand, by incandescence,
lights of moderate power, equal, for ex-
ample, to N or two gas-burners, can
be produced, and this would be Of course
a property of essential importance IN
any general use of electricity for domes-
tic lightning.
1t is on these subjects that several of
the most ingenious minds Of the day
are now working, and what we have
above stated not only gives the present
state of the problem, but will prepare
the reader to comprehend the new de-
velopments as they appear.
The next application Of Faraday's
discovery of magneto-induction is found
in the Bell telephone. In this instru-
ment a series Of electric currents are de-
veloped by the movements Of a thin
plate of iron in front of q steel magnet,
around whose end a wire is cooled. AS
the thin iron plate vibrates to the inn
pulse received from the voice of u
speaking near it, the lines Of force about
the magnet are caused to moye, and so
cut across the coils of wire, and conse
qIently develop III them electric cur
rents, These luctuating electric cur
rents, carried by a telegraph wire to a
distant place, modify as they vary, the
attraction of a similar magnet for Il like
thin iron plate, and thus this plate re-
peats the motions of the frat one, and
gives to the ear of the listener the mo.
tons which constitutes the sounds in the
spoken words uttered against the first
iron plate.
Notifications in form or arrangement
Of parts have been made by various ex-
perimenters and inventors, but the same
principle pervades all the telephones of
this class.