AN IMPROVED METHOD OF APPLYING ELECTRIC CURRENTS IN THE PRODUCTION OF LIGHT, AND LAMP EMPLOYED THEREFOR
Year: 1881

page_text: LETTERS PATENT to Sydney Pitt, of Sutton, in the County of Surrey, for
an Invention of "AN IMPROVED METHOD OF APPLYING ELECTRIC CURRENTS
IN THE PRODUCTION OF LIGHT, AND LAMP EMPLOYED THEREFOR." A
communication from abroad by Lucien Gaulard and John Dixon Gibbs, both
of Paris, in the Republic of France.
PROVISIONAL SPECIFICATION left by the said Sydney Pitt at the Office
of the Commissioners of Patents on the 11th November 1881.
"
SYDNEY PITT, of Sutton, in the County of Surrey. AN IMPROVED METHOD OF
APPLYING ELECTRIC CURRENTS IN THE PRODUCTION OF LIGHT, AND LAMP
EMPLOYED THEREFOR." [A communication from abroad by Lucien Gaulard and
John Dixon Gibbs, both of Paris, in the Republic of France.]
This Invention has for its object improvements in the application of electric
currents to the production of light.
The incandescent lamps at present in use give for the current employed a much
smaller return in light than can be obtained with the same current from an arc
lamp.
This phenomenon is believed to be due to the dynamo-electric machines
employed, producing electricity in its two states (dynamic and static), and that the
arc light, utilises these two states of electricity whilst the incandescent lamps
on the contrary only transform into light the dynamic force of the current
employed.
The proof of the reality of this observation, which is absolutely new and which
has led to the system of lighting herein after described, is that in vacuo the statical
spark passes whatever be the distance between the conductors.
Now in an arc lamp, the carbons being in contact and the resistance being
sufficient to cause them to become incandescent, the heat produced dilates the
surrounding air, a relative vacuum is then produced at the point of contact, and
on the carbons being separated the statical spark bursts out, forming the voltaic

page_text: arc which serves as a resisting conductor to the dynamic current, there are thus
two cooperating luminous effects.
In the case of the incandescent lamp on the contrary the statical charge of the
conductor passing directly returns to the machine and loses itself in the ambient
air without being utilised.
As a practical application of this principle a lamp is constructed in the following
manner:-
A carbon filament bent to the usual form is rendered incandescent by the
dynamic current of the circuit to which it is connected by platinum connectors.
Two conductors of platinum terminated at their upper ends by small spheres are
placed close to and in a nearly parallel vertical plane with the carbon filament, the
spheres at their extremities facing each other; these conductors receive the induced
current from a Rhumkorf coil placed upon the circuit.
Under these conditions the statical charge of the conductor exerting its influence
upon the fine wire of the coil produces an induced current in the latter which in
the form of a spark manifests itself between the spheres concurrently with the
incandescense. Thus the total quantity of electricity produced by the generator is
utilised.
This system of dynamical and statical conductors is enclosed in a glass globe in
which a vacuum is produced by ordinary methods.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Sydney Pitt in the Great Seal Patent Office on the 11th May
1882.
SYDNEY PITT, of Sutton, in the County of Surrey. "AN IMPROVED METHOD of
APPLYING ELECTRIC CURRENTS IN THE PRODUCTION OF LIGHT, AND LAMPS
EMPLOYED THEREFOR." A communication from abroad by Lucien Gaulard and
John Dixon Gibbs, both of Paris, in the Republic of France.
This Invention has for its object a new method of applying electric currents in
the production of light.
The incandescent lamps now constructed give for the value of the current
employed much less light than can be obtained with the same current by the aid
of an arc lamp.
It is believed that this phenomenon is due to the dynamo electric machines
employed as the source, producing a quantity of electricity determined by the
volume of the inducting wire, and under a tension dependent on the resistance of
this inductor the arc lamp utilizes both the quantity of electricity and its tension,
whilst the incandescent lamp on the contrary transforms into light only the volume
of the current produced.
To show the reality of this observation (which is absolutely new, and which
has led to the method of applying electric currents in the production of light
hereinafter described, and which is claimed) it should be remembered that in a
vacuum the static spark shews itself, whatever may be the distance between the
conductors. Now in the arc lamp the carbons being in contact and the resistance
being sufficient to causo incandescence in these carbons, the heat produced dilates
the surrounding air, a relative vacuum is produced at the point of contact, and
if the carbons are separated the tension of the current will be sufficient in giving
to it the static form for determining the production of the voltaic are which
serves as a resisting conductor of the current; there are thus two simultaneous
luminous effects.
In the case of the incandescent lamp on the contrary the static charge of the
current passes directly and goes back to the machine without being utilized.
As a practical application of this principle, a lamp is constructed according to
the following description and the Drawing annexed:
A carbon thread /, of which the extremities have been previously coppered in a
galvanic bath for the length of about a centimetre, is rendered incandescent by the
quantity of the current of the circuit with which it is connected by means of
pincers of platinum or other metal e, e. Two insulated platinum conductors p, p,
terminating in small spheres are placed parallel to and in a plane at right angles
to that of the wires k, k, their extremities facing each other at o.
The con-
ductors p, p, receive the induced current of a Rhumkorf bobbin placed upon
the circuit c.
In these conditions the static charge only of the conductor c acting by influence
upon the fine wire of the bobbin will determine in the latter an induced current
which in the form of a spark will manifest itself at o concurrently with the
ncandescence; thus the total quantity of electricity produced by the generator
s utilized.
As the Figure shows, the system of dynamic and static conductors is enclosed in
globe a in which a vacuum is produced by the ordinary processes.
I do not desire to confine myself to the arrangements shown, which are
utended only to exemplify the Invention, but I claim the new method, consisting

page_text: in the separation of the quantity and the tension of the current at a given point
in the circuit in view to the production of light, substantially as herein described.
In witness whereof, I, the said Sydney Pitt, have hereunto set my hand and
seal, this Tenth day of May, in the year of our Lord One thousand eight
hundred and eighty two.