IMPROVEMENTS IN ELECTRIC LAMPS
Year: 1879

page_text: PROVISIONAL SPECIFICATION left by Alexander Melville Clark at the Office
of the Commissioners of Patents on the 6th January 1879. A communication
from abroad by Eugène Ducretet, of the Firm of E. Ducretet and Company, of
Paris, France.
ALEXANDER MELVILLE CLARK, of Chancery Lane, in the County of Middle-
sex, Patent Agent. "IMPROVEMENTS IN ELECTRIC LAMPS." [A communication
from abroad by Eugène Ducretet, of the Firm of E. Ducretet and Company, of Paris,
France.]
This Invention consists more particularly in immersing the carbon or other
pencil electrode (or electrodes) in a column of mercury for the purpose of feeding
it up as it is consumed. The light may be produced either by incandescence or by
che voltaic arc, or both combined, and may be produced either in the open air in
front of reflectors or within a globe, or a receiver containing rarefied air, or a gas
of any kind under pressure, or otherwise, and constantly renewed or not. The
column of mercury does not act on a float in order to effectuate the feeding of the
electrodes, but acts by the difference of density, the electrodes being immersed
alinost their entire length in the mercurial column, and thus receiving an upward
impulse without the use of any mechanical adjunct.
The rate of feed may be regulated if desired by weighting the lower end of the
electrode more or less. The upward motion thus produced serves to feed the
clectrode or electrodes in a uniform and regular manner against a stop, by which
the motion is limited, and made to correspond to the rate of consumption of the
electrode. If the upward pressure be slight when the circuit is closed repulsion
takes place, owing to the repellent action of two consecutive portions of the same
current, a small luminous arc is produced, and a portion of the electrode or electrodes
becomes incandescent. The greater the upward pressure of the electrode the
smaller will be the arc, and the more intense the incandescence, these two effects
thus concurrently producing a vivid light. By this means one or more electrodes
of different lengths, sizes, and forms may be fed with the greatest regularity
without the assistance of any mechanism, and similarly one or more electrodes
contained either in the same or different mercurial reservoirs may be fed up to a
fixed point for producing a large focus of great intensity.
The stop represented at H in the accompanying Drawing would, in the generality
of cases, be made of metal or other conductor, but it might consist of some non-
conducting refractory material where it is intended to produce a different distribu-
tion of the electric current in the electrodes. It may also be of any other form

page_text: than that shown, that is to say, either straight, inclined, horizontal, vertical,
spherical, conical, cylindrical, or in the form of a disc or plate, &c.
It is shown in the example as cylindrical, and fixed in a horizontal position, but
it may have an intermittent or continuous motion and be mado automatic in its
nction.
The pencils or electrodes may be of any suitable form, and may be of metal or
other conductor of electricity, whether natural or artificial. A number of mercurial
columns insulated from one another may be employed together, the current passing
from one electrode to the other, producing either a voltaic arc or incandescence at
the point of contact.
With this system the resistance in the circuit is always equal, notwithstanding
the waste of the electrodes, and the consequent diminution in their length. The
portion of the electrode immersed in the mercury is not included in the circuit, but
only the part that is above the mercurial lovel, and which is always of the same
length, and forms the conductor between the surface of the mercury and the upper
electrode or stop. This system of lamp is well adapted to subdivide the electric
current into a number of lights.
Lamps may also be arranged with several electrodes immersed in the mercurial
column, and kept out of action until successively brought by electrical or mechanical
agency into contact with the stop in order to afford light for a long period. It is
also possible without complicating the arrangements to employ electrodes of all
lengths immersed in columns of mercury of considerable height.
The Drawing shows a simple form of lamp, which is at once strong, cheap, regular
in its action, and capable of using up the whole of the electrode or electrodes, it
being specially adapted for use in carriages, locomotives, and vessels, and in other
situations where the lamp would be subject to any shocks or jerks, but it will be
understood that the form and arrangement may be varied according to require-
inents. T, tube or cylinder made of iron in preference to any other metal filled
with mercury L, and provided with a discharge cock R at bottom. G is a metal,
porcelain, or other cap having a guide hole for each electrode C. The column is
preferably filled with mercury above the guide holes of the cap, as shown, in order
to protect them from dust, which may pass through the cover g¹.
The guides are removable to enable different kinds of electrodes to be used in
the same lamp. S, electrode for the holder or stop H; V, key for breaking or
closing the circuit, which may be arranged to introduce resistances or derivations
to prevent any variation in the intensity of the remainder of a number of lights
cach time one is extinguished; P, base sufficiently weighted; N, globe or other
envelope or receiver, as before mentioned.
The arrows indicate the direction of the current.
extinguished from any distance.
The lamp may be lighted or