AN IMPROVED ELECTRIC LAMP
Year: 1856

page_text: LETTERS PATENT to Joseph Lacassagne, Chemist, and Rodolphe Thiers,
Manufacturer, both of Lyons, in the Empire of france, for the Inven-
tion of "AN IMPROVED ELECTRIC LAMP."
Sealed the 27th March 1857, and dated the 20th October 1856.
PROVISIONAL SPECIFICATION left by the said Joseph Lacassagne and
Rodolphe Thiers, at the Office of the Commissioners of Patents, with
their Petition, on the 20th October 1856.
We JOSEPH LACASSAGNE, Chemist, and RODOLPHE THIERS, Manufacturer,
both of Lyons, in the Empire of France, do hereby declare the nature of the
said Invention for "AN IMPROVED ELECTRIC LAMP," to be as follows:-
Our Invention relates to the application of a column of mercury to raising
and sustaining the moveable and electrode or pole of the electric circuit,
whereby electric light is produced, and to regulating the action or pressure
of the column by the action of the current, and thereby rendering the lamp
self-acting, and capable of producing and maintaining the light. The
electrodes are of carbon, as usual. We support the lower and moveable one
by a float placed in a cistern of mercury, which has a rise equal to the travese
required for the electrode, a second cistern or reservoir containing a supply of
mercury is placed at a higher level. The upper cistern has a communication
with the lower or float cistern, the passage of which is opened and closed by

page_text: means of a valve, actuated by electric current producing the light. For
this purpose an electro-magnet is included in the circuit to the poles, of which
magnet a soft iron lever armature is opposed. The opposite or free end of
the lever armature is acted on by a permanent steel spring, which constantly
tends to separate the armature from the magnet; this spring, however, exerts
less force than the power of the magnet when the current is unimpaired.
The action of the lamp is this:-The lower electrode is adjusted with the
lower mercury cistern nearly empty, and is placed in connection with the
positive pole of the battery; the upper electrode is then adjusted and placed in
connection with the negative pole; the connection between the cistern is
now opened, until the lower electrode is floated up and rises to the proper
distance from the opposing electrode to complete the electric circuit and produce
the light. The current being thus established, and the several parts so adjusted,
the action of the lamp will continue; so soon as the combustion of the
electrode has proceeded so far as to impair the strength of the current, the
spring antagonistic to the electro-magnet will attain an ascendency over the
power of the magnet, and will open the valve closing the passage from the
upper to the lower cistern; the mercury will now flow into the lower cistern,
and will raise the float in that cistern, and so lift the float and electrode
again to a proper level. The renewed strength of the current thus produced
will increase the power of the electro-magnet, which will again overcome
the power of the antagonistic spring and will close the valve. The magnet
will maintain its ascendency so long as the current is unimpaired or un-
interrupted.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Joseph Lacassagne and Rodolphe Thiers in the Great Seal
Patent Office on the 20th April 1857.
TO ALL TO WHOM THESE PRESENTS SHALL COME, we, JOSEPH
LACASSAGNE, Chemist, and RODOLPHE THIERS, Manufacturer, both of Lyons,
in the Empire of France, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twentieth day of October, in the year of our Lord
One thousand eight hundred and fifty-six, in the twentieth year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto us, the said
Joseph Lacassagne and Rodolphe Thiers, Her special license that we, the said
Joseph Lacassagne and Rodolphe Thiers, our executors, administrators, and

page_text: assigns, or such others as we, the said Joseph Lacassagne and Rodolphe
Thiers, our executors, administrators, and assigns, should at any time agree
with, and no others, from time to time and at all times thereafter during
the term therein expressed, should and lawfully might make, use, exercise,
and vend, within the United Kingdom of Great Britain and Ireland, the
Channel Islands, and Isle of Man, an Invention for "AN IMPROVED ELECTRIC
LAMP," upon the condition (amongst others) that we, the said Joseph
Lacassagne & Rodolphe Thiers, our executors or administrators, by an
instrument in writing under our or their or one of their hands and seals,
should particularly describe and ascertain the nature of the said Invention,
and in what manner the same was to be performed, and cause the same to
be filed in the Great Seal Patent Office within six calendar months next
and immediately after the date of the said Letters Patent.
NOW KNOW YE, that we, the said Joseph Lacassagne and Rodolphe
Thiers, do hereby declare the nature of our said Invention, and in what
manner the same is to be performed, to be particularly described and ascer-
tained in and by the following statement, reference being had to the Sheet
of Drawings hereunto annexed, and to the letters and figures marked thereon,
(that is to say):
The object of our Invention is,-1st, to regulate and to keep constant the
space or distance which exists between the two electrodes of electric lights,
whatever may be the rapidity of the combustion or wasting of the carbon
or graphite of which they consist.
2ndly, to obtain this regular and constant separation of the electrodes by
self-acting means, operating by the action of the current which produces the
light, combined with the action of a spring, or with the action of a current
derived from the light current.
3rdly, to obviate the necessity of any daily regulating of the apparatus.
The è proper regulation being once established is self-acting, and does not vary
except when it may be desired, whatever may be the intensity of the electric
current.
These various results are obtained by the passage of mercury from a
reservoir into a receiving cylinder placed underneath. The tendency of the
mercury to rise in this cylinder lifts with little friction a piston supporting the
lower electrode, which approaches the upper electrode according as the mercury
of the reservoir flows down into the cylinder.
The action of the electrodes approaching each other is produced by means
of a valve opening and closing the tube communicating from the reservoir to
the cylinder. This tube passes through one of the soft iron arms of an electro-

page_text: magnet, which receives its magnetic action from the current producing the
light, and which shuts the valve by its action upon an armature of soft iron,
which it presses against the valve.
The armature which shuts the valve by the action of the current producing
the light is attracted in an opposite direction by a spring, or by a second
electro-magnet receiving magnetic action from the derived current, the
intensity of which is determined by the resistance offered to it by a coil
interposed for that purpose, consequently the passage of the mercury from
the reservoir to the cylinder tends to establish itself under the action of the
derived current, which opens the valve, and to be interrupted under the action
of the principal current, which closes it: the resistance afforded to the derived
current is invariable. The resistance afforded to the principal current
increases by the widening of the distance or space between the two electrodes,
and diminishes by their coming near to each other. If the distance between
them increases, the principal current meeting a greater resistance diminishes
in its intensity, which also diminishes the magnetic power of the electro-
magnet due from the principal current which closed the valve; the intensity
of the derived current (the resistance to which is invariable) increases in the
same ratio, and tends also by its action on the second electro-magnet to open
the valve.
If the electrodes approach each other the contrary effect is produced; the
principal current increases by the diminution of resistance through the
electrodes, while the derived current diminishes in the same proportion, and
tending to close the valve to prevent the further passage of the mercury.
It is then evident, that after having determined the resistance of the derived
current by the length of the wire of the resisting bobbin or coil, there will be
established between the two currents a kind of equilibrum, which will maintain
a passage for the exact quantity of mercury that should necessarily flow from
the reservoir to the electrode cylinder to lift and regulate the space between
the electrodes.
The annexed Drawing represents an electric lamp constructed according to
to our Invention.
Fig. 1 shows the elevation of the photo-electric lamp; Fig. 2 shows a
vertical central section; and Fig. 3, a plan of the self-acting regulating
part.
a, reservoir containing the mercury; b, receiving cylinder, receiving the
mercury from the reservoir a; in this receiving cylinder ba float is placed on
the mercury, consisting of an iron disc supporting a stem a which carries the
first electrode. c, c¹, electrodes of graphite or carbon; the second is adjusted

page_text: and fixed on the stem of the apparatus; its position may be varied as required
by means of a screw c¹. The first electrode is moveable, and is connected to
the rod of the float. d, flexible tube, furnished with a stop-cock, leading the
mercury from the reservoir a into the receiving cylinder b, but it first passes
through the regulating passage. c which is a piece of iron, having two vertical
passages, each connected by two horizontal parts with the two parts of
flexible tube d, d; f, india-rubber valve covering the upper end of the
two passages in the piece e; g, bobbins or coils, traversed by the principal
current; h, h, coils traversed by the derived current, producing the force
antagonistic to the first bobbins or coils g; i, soft iron armature; j, thumb
screw to limit the course of the armature i; k, reflector ;. m, positive con-
ductor to the upper electrode ;, n, negative conductor from the lower electrode
to the generator of electricity, passing through the bobbins or coils g; o, o,
conductors of the derived current in connection with the poles of the same
battery or generator of electricity, passing through the resisting coil d,
antagonistic to the electro-magnet g; connected with the conductor n at r.
Instead of the second electro-magnet h, a spring of a given strength,
antagonistic to the magnet g, g, may be used, and will answer the same
purpose.
Having described the nature of our Invention, and the manner in which
the same may be performed, we declare that what we claim as our Invention
is, the herein-before described photo-electric lamp, having the self-acting
power of regulating the distance between the electrodes by the current itself
by means of parts combined and arranged as herein-before described.
In witness whereof, we, the said Joseph Lacassagne and Rodolphe
Thiers, have hereunto set our hands and seals, this Sixteenth day
of April, in the year of our Lord One thousand eight hundred and
fifty-seven.