Since the month of May last, the concert at the Champs Elysées has been
lighted by sixteen voltaic arc lamps on a new and very simple system,
which gives excellent results in the installation under consideration.
The sixteen lamps are on the divisible system, and their regulation is
based upon the principle of derivation. They are supplied by a Siemens
alternating current machine and arranged in four circuits, on each of
which are mounted four lamps in series. The accompanying figures will
allow the reader to readily understand the system, which is as simple
as it is ingenious, and which has been combined by Mr. Mondos so as to
obtain a continuous and independent regulation of each lamp.
In this system the lower carbon is stationary, the luminous point
descending in measure as the carbons wear away through combustion. The
upper carbon descends by its own weight, and imperceptibly, so as to
keep the arc at its normal length.
The mechanism that controls the motions of the upper rod that supports
the carbon-holder consists of two bobbins of fine wire, E (Fig. 2),
mounted on a derived circuit on the terminals of the lamp; of a lever,
L, articulated at O, and supporting a tube, TT', and the whole movable
part balanced by a counterpoise, P. This lever, P, carries two soft iron
cores, F, which enter the bobbins, E, and become magnetized under the
influence of the current that passes through them. The upper part of
the tube, T, carries a square upon which is articulated at O' a second
lever, L', balanced by a second counterpoise, P', and carrying a flat
armature, _p_, opposite the cores, F', that are fixed to the first
horizontal lever, L. The carbon-holder rod, CC', slides freely in the
tube, TT', and is wedged therein by a small piece, _a m l_, fixed to
the lever, L'. For this reason the tube, TT', is provided with a notch
opposite the piece _a m l_, and the two arms, _a_ and _m_, of the latter
are shaped like a V, as may be seen in part in the plan in Fig. 2. It is
now easy to understand how the system operates; when the current is not
traversing the circuit, the carbons are separated; but, at the moment
the circuit is closed for lighting a series of lamps, it traverses the
electro-magnet, which then becomes very powerful, and draws down the
cores, F, along with the lever, L, the tube, TT', and the carbon-holder,
CC', and brings the carbons in contact. The arc then forms, and the
current divides between the arc and the bobbins, E. Its action upon the
cores, F, becomes weak, and it can no longer balance the counterpoise,
P, which falls back, and raises the system again. The arc thus
becomes _primed_. The cores, F, however, preserve a certain amount of
magnetization; the armature, _p_, is attracted, and the lever, L',
assumes a position of equilibrium such that the piece, _a m l_, wedges
the rod, CC', in the tube, TT', and holds it suspended. When, through
wear of the carbons, the arc elongates, a greater portion of the current
passes into the bobbins, E, the armature, _p_, is attracted with more
force, and the lever, L', swings around the point, O'. The rotation of
L' separates the piece, _a m l_, from the rod, CC', which, being thus
set free, slides by its own weight and shortens the arc. The current
then becomes weak in E, the armature, _p_, is not so strongly attracted,
the lever, L', pivots slightly around O' under the action of the weight,
P', and the brake or wedge enters the notch anew, and stops the descent
of the carbon. In practice, the motions that we have just described are
exceedingly slight; the carbon moves imperceptibly, and the length of
the arc remains invariable.
[Illustration: Fig. 1--MONDOS'S ELECTRIC LAMP.]
It will be seen, then, that the lever, L, and the tube, TT', serve
exclusively for _lighting_, and the lever, L', exclusively for
regulating the distance of the carbons.
This lamp exhibits great elasticity, and can operate, without a
change of any part of its mechanism, with currents of very different
intensities. It suffices for obtaining a proper working of the apparatus
in each case, to regulate the distance from the weight, P', to the point
of suspension, O', and the distance from the armature, _p_, to the
cores, F. At the Champs Elysées concerts the lamps are operating with
alternating currents; but they are capable of operating with continuous
ones also, although the slight tremor of the electro-magnetic system,
due to the use of alternating currents and as a consequence of rapid
changes of magnetization, seems in principle very favorable to systems
in which the descent of the carbon is based upon friction instead of a
clutch. At the Champs Elysées concerts the lamps burn crayons of 9 to
10 millimeters with a current of 9 to 10 amperes and an effective
electro-motive power of 60 volts per lamp. The light is very steady,
and the effect produced is most satisfactory. The dispensing with all
clock-work movement and regulating springs makes this electric lamp
of Mr. Mondos a simple and plain apparatus, capable of numerous
applications in the industries, in wide, open spaces, in all cases where
foci of medium intensity have to be employed, and where it is desired to
arrange several lamps in the same circuit.--_La Nature_.
[Illustration: Fig. 2--REGULATING MECHANISM.]
* * * * *
[AMERICAN POTTERY AND GLASSWARE REPORTER.]