IMPROVEMENTS IN ELECTRIC LIGHT APPARATUS
Year: 1877

page_text: LETTERS PATENT to Alexander Melville Clark, of 53, Chancery Lane, in the
County of Middlesex, Patent Agent, for the Invention of "IMPROVEMENTS IN
ELECTRIC LIGHT APPARATUS." A communication from abroad by the Firm of
Lontin and Company, of Paris, France.
Sealed the 6th November 1877, and dated the 29th May 1877.
'
PROVISIONAL SPECIFICATION left by the said Alexander Melville Clark at
the Office of the Commissioners of Patents on the 29th May 1877.
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of Middlesex,
Patent Agent. "IMPROVEMENTS IN ELECTRIC LIGHT APPARATUS." [A communica-
tion from abroad by the Firm of Lontin and Company, of Paris, France.]
This Invention relates to improved means of controlling, the mechanism for
regulating or maintaining at a uniform distance apart the carbon points of the electric
light. Such regulators may be roughly classed as being so constructed that the
carbon points are moved towards one another either automatically or by clockwork.
A special apparatus operated by the current is sometimes applied, either to arrest
the mechanism by which the carbons are fed up, or to part or distance the carbons,
and to effect this stoppage or separation, as the case may be, electro-magnets are
often employed which on the passage of the currents operate to produce this result.
This Invention consists, first, in the employment (in lieu of electro-magnets) of a
simple wire (or its equivalent), which by the passage of the current becomes heated,
and consequently expanded or extended in length, this alteration in the length of
the wire (or its equivalent) being applied to control the action of the various kinds
of mechanism used for regulating the electric light. The wire should be of such a
gauge that by the passage of the current it may be heated to, say, 400° C. as.a
maximum. If by heating a proper length of wire a sufficient degree of extension is
attained, it will be readily understood how, by connecting the wire to a lever or
other organ capable of being oscillated by the tension of a counter spring, the
extension of the wire may be made either to cause the arrest of the mechanism by
which the carbons are fed together, or to part or distance them, according to the
kind of regulator employed.

page_text: It will be obvious that a strip of metal of any form may be substituted for the
wire, provided that its section is such that it will attain a sufficiently high tem-
perature and the necessary amount of expansion.
In order to understand how the extension of a wire is capable of producing the
necessary movements for controlling the regulating meclianism of the carbons,
suppose a silver wire 20 centimetres in length to be used. Under the action of a
current from a source of electricity of sufficient power the wire becomes heated to a
temperature of, say, 400° C., and is lengthened to the extent of 2 millimetres. This
wire if placed in an electric light regulator would be quite adequate to produce the
movements necessary for the proper working of the regulator, especially as in pro-
portion as the luminous arc lengthens the intensity of the current passing through
the carbons decreases. Therefore when the arc has increased in length the wire
may be at 150° or 200 only, which would cause a contraction of 10 to 14/10 ths of a
millimetre.
The length of the wire will of course be such as to produce the amount of motion
necessary for the proper working of the regulators. As the silver wire under the
influence of different currents might produce arcs of too great difference to produce
a perfect light this objection may be avoided by the employment of a supplementary
part, consisting of a solenoid or electro-magnet, whose wire by its fineness has a
very high resistance. The two ends of the wire of this coil are attached either
directly or indirectly to the two carbon holders, so that if the carbons are in contact,
or if the arc be very short, the coil will be almost entirely inactive, its activity
increasing proportionately as the length of the arc becomes greater.
If the action of the coil be balanced by a spring capable of being regulated at
will, it may be so arranged as to become active immediately the luminous arc
attains a certain length.
The action of the coil may be applied in various ways; for instance, either to
release the mechanism by which the carbons are fed together (the mechanism being
actuated by a spring barrel or weight), or bring into action a commutator, having
for its object to effect mechanically or directly the connection of the two ends of the
expanding wire. Both these effects may be obtained with the same solenoid, either
together or separately, thus providing the most perfect means of regulating,.the
electric light.
The Invention thus consists in the use of a wire to produce the separation in the
regulators of electric lights, and the employment of a solenoid or electro-magnet to
effect the release of the mechanism by which the carbons are fed up, the solenoid or
electro-magnet being excited by the derivation of the direct lighting current. It
will be evident that this solenoid or electro-magnet would alone suffice were the
regulator so constructed as to automatically separate the carbon points. Thus the
solenoid may be applied to all kinds of regulators in which the separation of the
carbons is constantly maintained. By this means an arc of constant length may be
'obtained; inasmuch as the derivation in the solenoids or fine wire electro-magnets
of very high resistance only allows the current to pass at the moment when the
amplitude of the arc is sufficient to bring it in equilibrium with the resistance of
the solenoid or electro-magnet. But as it may happen that by the consumption or
breakage of the carbons, or by any other accidental cause liable to stop the working
of the motor, the arc might not be re-established, in which case the derivation from
the lighting current passing through the coil would increase to such a degree as to
destroy the coil. This may be remedied in the following manner:-The ingress
wire of the derived current in the coil or electro-magnet is interrupted for about
the length of two or three centimetres, and replaced by a very fine wire, which is
readily inserted in split studs provided for the purpose. In the event of the accident
foreseen, and to be provided against, this wire, which is selected of a size and nature
suitable for the purpose, will be fused by the current, so that the circuit is, at once
interrupted.
In order to restore the working of the apparatus it is only necessary to, replace
the fused wire by another piece of the same kind. This feature of the Invention
"

page_text: -
may be utilized in another way in order to realize another and important improve-
ment, which I will now describe.
In the application of the electric light for lighting purposes, it often happens that
the unit of light adopted in the machine is too powerful in relation to the space to
be lighted, and it follows that it is not only of advantage but also necessary to
divide this unit by introducing several regulators in the same circuit, and con-
sequently by producing several luminous arcs. This method of dividing the circuit
has already been attempted long since, but failed with the apparatus employed
owing to the simultaneous extinction of all the lights placed in the same circuit
when any one of the regulators failed to work. Moreover, it was sought to employ
it in a general manner for dividing the single current then obtainable, whereas (as:
has been already observed) it is here proposed to realize it in connection with one
only of the currents of the Lontin machine, and in special cases only. Where this
division becomes too great it is preferred to employ multiple currents and
independent regulators.
The following is the mode in which the division is effected in the improved
regulators of this Invention:-The fusible wire above mentioned retains so long as
it remains intact a commutator of any suitable kind, but immediately the wire is'
fused the commutator comes into use and allows the current to continue to support
the other lights, while the one which has become extinguished is re-adjusted. The
function of this commutator is to close the circuit in such manner that the current
passes directly between the adjacent regulators.
The fusible wire may be employed either for the purpose first above described, or
simply for controlling the operation of the commutators of all the apparatus pro-
ducing the electric light by the voltaic arc, or otherwise, which are placed in the
same circuit.
The above system permits of dividing each of the partial currents produced by
the Lontin machines so far as these currents admit, this being preferable to
lowering the unit of the current too much.
In certain cases the fusible wire may be replaced by means of a uni-metallic or
multi-metallic organ, whose expansion will produce such variations in length or
form as will retain the commutators out of or put them in action. This arrange.
ment offers the further advantage of avoiding the necessity of replacing the fused
wire, and it may sometimes serve alone as a commutator. The solenoid or electro-
magnet may be applied to all kinds of known regulators.
In the Foucault, Serrin, and others of the same kind, only one solenoid or electro-
magnet may be used, while in others wherein two independent trains are used, which
are set in motion separately by two distinct electro-inagnets, one for the convergence
and the other for the separation of the carbons, it is preferable to employ two solenoids
or electro-magnets, as above described.
In connection with the employment of resistance, solenoids or electro-magnets
above mentioned for controlling a number of regulators in the same circuit, I have
specified the use of metallic wires, which at the moment of rupture, 'under the
influence of the heat developed by too prolonged a passage of the lightning current
effect contacts whereby the communication of the current with the other regulators
is maintained. This precaution might be necessary to prevent overheating of the
resistance coils, and the possible extinction of all the lights in the same circuit should
any one cease working owing to an accident of any kind, such as the breakage of
the carbon points, for instance.
Experience has shown that a much greater number of regulators may be intro-
duced in the same circuit than was at first supposed possible. In principle it is
only necessary to increase or diminish the amount or length of the resistance. The
special mode of application for this purpose constitutes another feature of improve-
ment. The resistance for each regulator is so arranged as to modify at will the
quantity of the current circulating therein, and that in such a way that any one of
the regulators placed in the same circuit, whether coupled with one, two, three, or
other number of regulators may in all cases and instantaneously operate under the

page_text: same conditions of resistance as if alone, this result being effected by the action of a
single commutator.
Among the many arrangements which may be adopted for the purpose, one
example is here given. This consists in winding on the resistance bobbin a cable
composed of several insulated wires, instead of a single wire only. By leaving the
ingress and egress ends of each free, they may be subsequently connected, according
to requirements, in such a way that for a given number of regulators placed in the
same circuit, the sum of the resulting resistances may be reduced to that of one
single regulator. In other words the resistance will be rendered constant, whatever
may be the number of regulators introduced in the same circuit. It is then only
necessary to connect the ingress and egress ends of the wires with a commutator
suitably arranged to at once effect the combination desired.
In Figure 1 of the Drawings accompanying this Specification, the electro-magnet
for effecting the release of the mechanism is separated from the resistance coil, as
the size of the latter (if the number of wires composing it is considerable) might be
such as to make it inconvenient to place it amongst the mechanism. In this case it
is preferable to wind the wire in a flat coil upon a card, and place it in a hollow
base beneath the apparatus, as in the case of the condenser of the Ruhmkorff coil.
The wires wound either separately or in the form of a cable are shown in Figure 1,
three in number only, as an example. The ingress end a, b, c, and the egress end a¹,
b¹, c¹, are connected to contact, as indicated.
The arms indicated by dotted lines communicate with each other, as do also those
represented by unbroken lines, but the one set is insulated from the other. It will
thus be seen that by placing the arms in the position No. 1, Figure 2, there will be
a resistance of one wire a, a¹, only, the two others being quite inoperative; such
would be the case when a single regulator only is in use. In position No. 2, the
two wires a, a, b, b', constitute the resistance, which is consequently reduced to one
half in each regulator, the third wire remaining unused. Such is the arrangement
adopted where two regulators are placed in the same circuit; it will be seen that each
having a resistance one half less, the sum of the two resistances will be the same
as when one regulator only is in work. Similarly, it will be seen that the
position No. 3 gives for each regulator a resistance three times weaker than position
No. 1, and is suited for three regulators operating in the circuit, as the sum of the
three resistances is still of the same value as in the first and second cases
mentioned. The other positions, Nos. 4, 5, and 6, Figure 2, sufficiently indicate
the results which may be obtained and utilised in case of need.
It will be understood that the commutator above described may either be placed
on an insulated plate at the front of the apparatus, or if desired be removed together
with the resistance coil to a manipulator at a distance, at which also the safety wire
will be placed.
The application of these arrangements, combined with the safety wire above
described for the simultaneous and regular working of several regulators in the
same circuit, thus constitutes a part of this Invention, which thus affords a
practical means of effecting the division of the electric light hitherto considéred
impracticable.
It has been stated above that a single coil would generally be sufficient, but that
it might be sometimes preferable to use two, one for the approach, and the other for
the separation of the carbon points, as, for instance, where the regulators have two
independent trains of clockwork, although not confined to this case only.
The following is the arrangement-In place of a resistance coil or electro-
magnet with coils of fine wire, I use an electro-magnet N, Figure 3, on which
the wire traversed by the light current is wound, as in most regulators, but instead
of placing it directly in the circuit of the light wire, as in Figure 4, it is placed
in a derivation thereof, Figure 3, the two points of derivation being on the same
side of a carbon. In order, however, to cause the light current to pass through this
electro-magnet, a resistance P of wire of the same thickness as that of the light
circuit is interposed between the two points of derivation, the length of said wire P

page_text: being sufficient to about equally divide the derivation between the two circuits.
This arrangement is employed for the purposes of the separation of the carbons
(which are moved towards one another by the electro-magnet M, and the com-
plementary resistance coil above mentioned) as this second electro-magnet is thus
rendered independent of the lighting current, if it is desired to act directly on
the former by a means of graduating the current which traverses it. This is in
effect what is done. Figure 6 shows such a means.
Figure 7 represents another arrangement for obtaining a similar result. This
consists of a graduating commutator placed at point B, Figure 5, whose function is
to permit the derivation by the wire f of a greater or less amount of the total
current which arrives by wire g, and thus admit of an exact regulation of the effect
produced by electro-magnet N.
The Drawing shows sufficiently the action of the commutator without further
description. This arrangement may also be combined with a manipulator at a
distance, as shown in Figure 8, in such a way that the latter may also receive the
safety wire resistance coil, and resistance commutator, above described. The latter
is however oniitted from Figure 8. A stud may also be provided on the manipulator
for bringing the carbons together by hand when the safety wire fuses.
It has been shown how, on the fusing of the wire, the communication of the current
with the remainder of the regulators is preserved. This additional stud or button
will admit in the majority of cases of re-lighting by hand and at a distance the
regulator which has become extinguished, and immediately restoring everything to
working order.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Alexander Melville Clark in the Great Seal Patent Office on the 28th
November 1877.
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of Middlesex,
Patent Agent. "IMPROVEMENTS IN ELECTRIC LIGHT APPARATUS." A communica-
tion from abroad by the Firm of Lontin and Company, of Paris, France.
This Invention relates to improved means of controlling the mechanism for
regulating or maintaining at a uniform distance apart the carbon points of the
electric light. Such regulators may be roughly classed as being so constructed that
the carbon points are moved towards one another either automatically or by clock-
work. A special apparatus operated by the current is sometimes applied either to
arrest the mechanism by which the carbons are fed up, or to part or distance the
carbons, and to effect this stoppage or separation, as the case may be, electro-magnets
are often employed, which, on the passage of the currents, operate to produce this
result.
This Invention consists, first, in the employment (in lieu of electro-magnets) of a
simple wire (or its equivalent), which by the passage of the current becomes heated
and consequently expanded or extended in length, this alteration in the length of
the wire, or its equivalent, being applied to control the action of the various kinds
of mechanism used for regulating the electric light. The wire should be of such a
gauge that by the passage of the current it may be heated to, say, 400° Cent, as a

page_text: #
maximum. If by heating a proper length of wire a sufficient degree of extension
is attained, it will be readily understood how, by connecting the wire to a lever or
other organ capable of being oscillated by the tension of an opposing spring, the
extension of the wire may be made either to cause the arrest of the mechanism by
which the carbons are fed together, or to part or distance the carbons, according to
the kind of regulator employed..
It will be obvious that a strip of metal of any form may be substituted for the
wire, provided that its cross sectional area is such that it will attain a sufficiently
high temperature and the necessary amount of expansion.
In order to understand how the extension of a wire is capable of producing the
necessary movements for controlling the regulating mechanism of the carbons,
suppose a silver wire 20 centimetres in length to be used. Under the action of a
current from a source of electricity of sufficient power the wire becomes heated to a
temperature of, say 400° Cent., and is lengthened to the extent of two millimetres.
This wire if placed in an electric light regulator would be quite adequate to
produce the movements necessary for the proper working of the regulator, especially
as in proportion as the luminous arc lengthens the intensity of the current passing
through the carbons decreases. Therefore when the arc has increased in length the
wire may be at 150° or 200°, only which would cause a contraction of 10 to 1/10 the
of a millimetre: Such a variation in the length of the wire is sufficient to ensure
the proper working of all electric light regulators, whatever may be their arrange-
ment, it being understood that the wire should be of such length as will ensure the
necessary amount of motion.
The Invention thus consists, 1st, in the use of a wire which is heated and
dilated or varied in length by the passage of the current for the purpose of
regulating electric light apparatus generally. As the silver wire under the influence
of different currents might produce arcs of too great difference in size to ensure a
perfect light, this objection may be obviated by the employment of a supplementary
part consisting of a solenoid or electro-magnet whose wire, owing to its fineness, has
à very high resistance; the two ends of the wire of this coil are attached either
directly or indirectly to the two carbon holders, so that if the carbons are in contact,
or if the arc be very short, the coil will be almost entirely inactive, its activity
increasing proportionately as the length of the are becomes greater.
If the action of the coil be balanced by a spring capable of being regulated at
will, it may be so arranged as to become active immediately the luminous arc attains
a certain length.
The action of the coil may be applied in various ways, for instance, either to
release the mechanism by which the carbons are fed together (the mechanism being
actuated by a spring barrel or weight) or bring into action a commutator having
for its object to effect mechanically or directly the approximation of the two ends of
the expanding wire. Both of these effects may be obtained with the same solenoid,
either together or separately, thus providing the most perfect means of regulating
the electric light.
The Invention thus also consists in the use in electric light-regulators, of a wire
or its equivalent, heated and dilated by the current as above specified to produce
the separation of the carbons in combination with a solenoid or electro-magnet to
effect the release of the mechanism by which the carbons are fed together, the
solenoid or electro-magnet being excited by the derivation of the direct lighting
current.
It will be evident that this solenoid or electro-magnet would alone suffice were
the regulator so constructed as to automatically effect the separation of the carbon
points, and the Invention also consists in so using it, and in other improvements
hereafter specified. The solenoid may thus be applied to all kinds of regulators in
'which the separation of the carbons is constantly maintained, such as those of
Foucault and others. By this means an arc of constant length may be obtained, as
the dérivation in the solenoids or electro-magnets having a very high resistance
only allows the passage of the current, calculated according to the requirements of

page_text: the case, when the arc has attained a length sufficient to equal the resistance of the
solenoid or electro-magnet.
As it may happen that owing to the total consumption or the breakage of the
carbons, or to any other accidental cause liable to stop the working of the motor by
which the carbons are approximated, the arc might not be re-established, and the
derivation from the lighting current passing through the coil might consequently
increase to such a degree as to destroy the coil, the following safety device is adopted
to guard against this result.
At the ingress end of the derived circuit to the coil or electro-magnet is interposed
a very fine wire about 2 or 3 centimetres in length, which is readily inserted in
split studs provided for the purpose, so that in the contingency above mentioned,
this wire, which is selected of a size and nature suitable for the purpose, will be
fused by the current, so that the circuit is at once completely interrupted.
In order to restore the working of the apparatus it is simply necessary to replace
the fused wire by another of the same kind. This feature of the Invention may be
utilised in another way in order to realise another and important improvement,
which I will now describe.
In the application of the electric light for lighting purposes it often happens that
the unity of light adopted in the machine is too powerful in relation to the space to
be lighted, and it follows that it is not only of advantage, but even necessary, to
divide this unity by passing the same current through several regulators, and
producing several luminous arcs. This method of dividing the circuit has already
been attempted long since, but failed with the apparatus employed owing to the
simultaneous extinction of all the lights in the same circuit when any one of the
regulators ceased to work. Moreover, it was sought to employ it in a general
manner for dividing the single current then obtainable, whereas (as has been already
observed) it is here proposed to utilise it in connection with one only of the currents
of the Lontin machine, and in special cases. Where this division becomes too great,
it is preferred to employ multiple currents and independent regulators.
The following is the mode in which the division is effected in the improved
regulators of this Invention :-The fusible wire above mentioned so long as it
remains intact retains a commutator of any suitable kind, but immediately the
wire is fused the commutator comes into use and allows the current to continue to
support the other lights while the one which has become extinguished is being
readjusted. The function of this commutator is thus to close the circuit so that
the current passes direct from the regulator before to the one after it.
The fusible wire may be employed either for the purpose first above described,
or simply for controlling the operation of the commutators, of all the apparatus
producing the electric light (by the voltaic are or otherwise) which are placed in
the same circuit.
The above system permits of dividing each of the partial currents produced by
the Lontin machines, so far as these currents admit, this being preferable to
lowering the unit of the current too much.
In certain cases the fusible wire may be replaced by means of a uni-metallic or
multi-metallic device, whose expansion will produce such variations in length.or
form as will retain the commutators out of or put them in action, as the case may
be. This arrangement offers the further advantage of avoiding the necessity of
replacing the fused wire, and it may sometimes serve alone as a commutator. The
solenoid or electro-magnet may be applied to all kinds of known regulators.
In the Foucault, Serrin, and other regulators of the same kind, only one solenoid
or electro-magnet may be used, while in others, wherein two independent trains
are used which are set in motion separately by two distinct electro-magnets, one for
the convergence and the other for the separation of the carbons, it is preferable to
employ two solenoids or electro-magnets, as above described.
In connection with the employment of resistance solenoids or electro-magnets
above mentioned for controlling a number of regulators in the same circuit I have
specified the use of metallic wires, which, at the moment of their rupture. under-

page_text: the influence of the heat developed by too prolonged a passage of the lighting
current, effect contacts whereby the communication of the current with the other
regulators is maintained. This precaution might be necessary to prevent over-
heating of the resistance coils, and the possible extinction of all the lights in the
same circuit, should any one cease working owing to an accident of any kind, such
as the breakage of of the carbon points, for instance. By this means the remainder
of the lights will continue uninterruptedly in action.
Experience has shown that a much greater number of regulators may be
introduced in the same circuit than was at first supposed possible. In principle it
is only necessary to increase or diminish the size or the length of the wire of the
resistance coil. The special mode of application for this purpose constitutes another
feature of improvement. The resistance coil for each regulator is so arranged as to
modify at will the quantity of the current circulating therein, and that in such a
way that any one of the regulators placed in the same circuit, whether coupled
with one, two, three, or other number of regulators, may in all cases, and instan-
taneously, operate under the same conditions of resistance as if alone, this result
being effected by the action of a single commutator.
Among the many arrangements which may be adopted for the purpose, one
example is here given; this consists in making the resistance coil of a cable
composed of several insulated wires, instead of a single wire only. By leaving the
ingress and egress ends of each free they may be subsequently connected according
to requirements, in such a way that for a given number of regulators placed in the
same circuit, the sum of the resulting resistances may be reduced to that of one
single regulator. In other words, the resistance will be rendered constant whatever
inay be the number of regulators introduced in the same circuit. It is then only
necessary to connect the ingress and egress ends of the wires with a cominutator
suitably arranged to at once effect the combination desired.
In Figure 1 of the Drawings accompanying this Specification, the electro-magnet,
for effecting the release of the mechanism for feeding the carbons, is separated from
the resistance coil, as the size of the latter (if the number of wires composing it be
considerable) might be such as to make it convenient to place amongst the
mechanism. In this case it is preferable to wind the wire in a flat coil upon a card,
and place it in a hollow base beneath the apparatus, as in the case of the condenser of
the Ruhmkorff coil. The wires wound either separately, or in the form of a cable, are
shown in Figure 1 as three in number only, as an example. The ingress ends a, b, c,
and the egress ends a, b, c¹, are connected to contacts as indicated.
The arms indicated by dotted lines communicate with each other, as likewise
those represented by unbroken lines, but the one set is insulated from the other.
It will thus be seen that by placing the arms in the position No. 1, Figure 2, the
resistance will consist of a single wire a, a¹, the two others being quite inoperative;
such would be the case when a single regulator only is in use. In position No. 2
the two wires a, a, b, b¹, constitute the resistance, which is consequently reduced
to one-half in each regulator, the third wire remaining unused. Such is the
arrangement adopted where two regulators are placed in the same circuit; it will
be seen that each having a resistance one-half less, the sum of the two resistances
will be the same as when one regulator only is in work. Similarly, it will be seen
that the position No. 3 gives for each regulator a resistance three times weaker
than position No. 1, and is suited for three regulators operating in the circuit as the
sum of the three resistances, is still of the same value as in the first and second
cases mentioned. The other positions, Nos. 4, 5, and 6, Figure 2, sufficiently
indicate the results which may be obtained and utilised in case of need.
The commutator, above described may either be placed on an insulated plate at
the front of the apparatus, or; if desired, be removed, together with the resistance
coil, to a manipulator at a distance, on which also the safety wire will be placed.
The application of these arrangements, combined with the safety wire above
.described, for the simultaneous and regular working of several regulators in the
same circuit, thus constitute improvements affording a practical means of effecting

page_text: the subdivision of the electric light, which has been hitherto, considered im-
practicable.
It has been stated above that a single coil would generally be sufficient, but that
it might be sometimes preferable to use two, one for the approximation and the
other for the separation of the carbon points; as, for instance; where the
regulators have two independent trains of clockwork, although not confined to this
case only.
The following is the arrangement adopted in this case:-In place of a resistance
coil or electro-magnet, with coils of fine wire, I use an electro-magnet N, Figure 3,
on which the wire traversed by the lighting current is wound, as in most regulators; .
but instead of placing it directly in the circuit of the lighting current, as in Figure 4,
it is placed in a derivation thereof, Figure 3, the two points of derivation being on
the same side of a carbon; and in order to cause the lighting current to pass
through this electro-magnet, a resistance P of wire of the same thickness as that of
the circuit of the lighting current is interposed between the two points of derivation,
the length of the said wire P being such that the current is about equally divided
between the two circuits. This arrangement is employed. for the parting of the
carbons (which are moved towards one another by the electro-magnet M; and the
complementary resistance coil above mentioned), as this second electro-magnet is
thus rendered independent of the lighting, current, if it is desired to act directly
on the former by a means of graduating the current which traverses it; this is in
effect what is done. Figure 6 shows such a means, and Figure 7 represents another
arrangement for obtaining a similar result. This consists of a graduating .com-
mutator placed at point B, Figure 5, whose function is to permit the derivation by
the wire f of a greater or less amount of the total current which arrives by, wiré.g,
and thus admit of an exact regulation of the effect produced by electro-magnet N.
The drawing shows sufficiently the action of the commutator without further
description, and in Figure 5 it is shown in its place. This arrangement"
may also
be combined with a manipulator at a distance, as shown in Figure 8, in such a way
that the latter may also receive the safety wire, resistance coil, and resistance
commutator above described.. The latter is however omitted from Figure 8. A
stud may also be provided on the manipulator for bringing the carbons together by
hand when the safety wire, fuses.
It has been shown how on the fusing of the wire the communication of the
current with the remainder of the regulators remains intact, and this additional
stud or button will admit in the majority of cases of establishing by hand and from
a distance the light which has become extinguished and of immediately restoring
everything to working order.
Having thus set forth the principal features of the Invention, it only remains to
point out, with reference to the resistance solenoid or electro-magnet placed in
derivation on either side of the luminous centre, that the action of this organ is
quite the reverse of that of the electro-magnets ordinarily employed in other electric
light regulators. Thus in the Serrin, Lontin, Foucault, Spakonski, Carré, and other
apparatus, the electro-magnets are of sufficiently coarse wire to allow of the passage of
the whole of the lighting current in the circuit of which they are placed. Moreover
the function of these magnets is by attracting their armatures to throw the regulating
apparatus into gear, whereas the reverse is the case in this instance.
Lastly, I would remark that the application of the resistance coil herein
described, does not necessarily entail the suppression of any part of existing
apparatus nor even of the electro-magnets ordinarily employed.
Having described the nature of the said Invention, and the manner of performing
the same, I declare that what I claim as the Invention to be protected by the
herein-before in part recited Letters Patent is,-
1st. The use of a wire, a strip of metal or its equivalent traversed by the current,
and dilated or contracted according to the greater or less intensity of the current,
the variations in its length thereby produced being applied to effect either

page_text: directly or indirectly the separation or approximation of the carbons, substantially
as specified.
2nd. The use of a metallic wire or strip for parting the carbons, in combination
with a resistance solenoid or electro-magnet excited by a derivation from the direct
current which produces the light, for releasing the mechanism by which the carbons
are approximated, substantially as specified.
3rd. The use of a solenoid or electro-magnet for approximating the carbons in
those regulators in which the parting of the carbons is effected automatically,
substantially as specified.
4th. The use of the said solenoids or electro-magnets for operating several
regulators in the same circuit, substantially as specified.
5th. The safety device applied, as herein described, consisting of a wire or metal
strip of such a size or nature as to be fused, and so break the connection when the
current from any cause becomes so intense as to injure or destroy the resistance
.electro-magnet or solenoid, the fusion of the wire also serving to bring into action a
commutator, which electrically isolates this regulator from the others in the circuit,
substantially as specified.
6th. The interposition in a derivation of the current of a strip, wire, or other
uni-metallic or multi-metallic organ, which by its dilatation or extension under the
influence of the current brings into action a commutator that electrically isolates
the regulator from the rest under the circumstances referred to in the previous claim,
substantially as specified.
7th. The arrangements described and shown in Figures 1 and 2 for varying at
will the resistance of the solenoid or electro-magnet in order to regulate the
· whole of the apparatus in the same circuit.
In witness whereof, I, the said Alexander Melville Clark, have hereunto set
my hand and seal, this Twenty-eighth day of November, in the year of our
Lord One thousand eight hundred and seventy-seven.