AN IMPROVED PROCESS OR METHOD OF PREPARING CARBON AND OTHER CONDUCTORS TO BE USED FOR ELECTRIC LIGHTING AND OTHER PURPOSES
Year: 1881

page_text: LETTERS PATENT to William Robert Lake, of the Firm of Haseltine, Lake,
and Co., Patent Agents, Southampton Buildings, London, for an Invention of
"AN IMPROVED PROCESS OR METHOD OF PREPARING CARBON AND OTHER
CONDUCTORS TO BE USED FOR ELECTRIC LIGHTING AND OTHER PURPOSES."
A communication from abroad by Hiram Stevens Maxim, of Brooklyn, New
York, United States of America.
PROVISIONAL SPECIFICATION left by the said William Robert Lake at
the Office of the Commissioners of Patents on the 15th February 1881.
WILLIAM ROBERT LAKE, of the Firm of Haseltine, Lake, and Co., Patent Agents,
Southampton Buildings, London. "AN IMPROVED PROCESS OR METHOD OF
PREPARING CARBON AND OTHER CONDUCTORS TO BE USED FOR ELECTRIC
LIGHTING AND OTHER PURPOSES." [A communication from abroad by Hiram
Stevens Maxim, of Brooklyn, New York, United States of America.]
This Invention relates to an improved method or process of preparing carbon or
similar material for electric lamps or lighting apparatus, or for other electrical
purposes, and is chiefly designed for use with lamps of that class known as
incandescent, in which the light-giving portion is a continuous conductor of high
resistance, commonly of carbon.
The objects of the said Invention are to make such carbon conductors of a
uniform standard illuminating power, and to make them more dense and homogenous
in structure and more elastic than those made by processes heretofore in use with a
resulting increase of durability.
By the modes heretofore generally practised for the making of electric carbons it
is impossible to obtain any considerable number which under a current of given
intensity will develop the same light. Where the conductors are made of the
carbon deposits formed on the interior of gas-retorts, whether by shaping such
carbon into the required form with cutting tools or by grinding it up and then
moulding it into shape under pressure, it is practically impossible to secure two
conductors having precisely the same radiating surface or the same resistance.
The same difficulty attends the ordinary modes of manufacturing incandescent
conductors by shaping a fibrous material into the desired form, and then carbonizing
it. Differences in the superficial area of the carbons or in their resistance will
produce corresponding differences in their relative illuminating power.
Manifestly in any system of electric lighting equality of light giving capacity in
the lamps employed is an object exceedingly desirable. The mode by which this

page_text: result may be attained, and which constitutes a part of the present Invention,
consists generally stated in subjecting the carbon conductor while surrounded by
an atmosphere of hydro-carbon vapor or other carbonaceous gas to the action of an
electric current in the presence of some standard light or other means of
determining when the conductor conforms to the standard fixed. The intense heat
generated by the passage of the current dissociates the elements of the gas, and the
carbon set free therefrom is deposited in a state of exceedingly minute subdivision
in the pores and upon the exterior of the carbon under treatment, gradually
reducing its resistance and correspondingly changing its illuminating capacity.
When this has been brought to the desired point, as indicated by the standard of
comparison; the operation of building up is arrested, and the finished carbon is
ready to be sealed up in the globe in which it is to be used.
The best means heretofore discovered for regulating the extent of the change to
be effected in the resistance of electric carbons in order to produce uniformity of
illuminating power is to use a standard electric lamp, connecting it with the circuit
in the same manner as the.carbon to be treated.
In carrying this Invention into practice a standard lamp is placed in a branch
between the main wires of the circuit and the carbon to be treated is arranged in
a co-ordinate branch between the two main wires. These branches are provided
with switches of any known and suitable character. The carbon to be treated is
approximately of the same size as that of the standard lamp, but is of higher
resistance, and is enclosed in a glass receiver whose only outlet is a tube.
Through this tube the globe is attached to an exhausting pipe by any tight
connection, preferably a joint of ground glass and a mercury seal. A tube leads to
an exhausting apparatus capable of producing a high vacuum, such, for instance, as
a "Sprengel" or a "Geissler" pump. There is a vessel containing gasoline or some
other very volatile hydro-carbon oil. This vessel may be filled through a tube
which should be hermetically sealed by a ground glass stopper or otherwise; the
vessel communicates with the pump through pipes and a cock. All the joints and
connections should be perfectly tight to prevent all ingress of air.
The cock being closed the air is exhausted from the globe as perfectly as
possible after which a current of electricity may be passed through the
conductor to be treated in order to expel from it the occluded gases which should
also be pumped from the globe. Then upon opening the cock the vapor of gasoline
will flow from the gasoline vessel into the globe, filling it to the required degree;
practically, a pressure of about an inch of mercury, more or less, will be found
sufficient. Now, inasmuch as the carbon or conductor to be treated is a higher
resistance than the standard lamp, it will be found upon switching the current to
the conductor and the lamp that a smaller portion of the current will flow through
the carbon than through the lamp, and the light developed in it will be
correspondingly less; but as the carbon or conductor builds up by the deposition
upon it of carbon from the surrounding gas, as above explained, its resistance
gradually falls, permitting an increased flow of the current through it, and
correspondingly increasing its illuminating power. When the light has become
equal to that of the standard lamp the operation is to be arrested.
Instead of arranging the standard lamp and the carbon to be treated in parallel
series in branches of the main circuit, as above described, they may be arranged in
consecutive series in the main circuit. In this case as the entire current would be
made to pass through both the carbon and the standard lamp, the light at first
developed in the carbon will, by reason of the greater resistance of the carbon, be
greater than that of the lamp; but as the building up of the carbon by the
decomposition of the surrounding gas proceeds, with a corresponding diminution
in its resistance, the heat and the light developed by the passage of the current
will gradually be diminished until the latter is brought to the same intensity as
that of the standard lamp.
Another mode of accomplishing the same result is to subject the carbons to be
treated to the action of a constant or uniform electric current, comparing the

page_text: changing intensity of the light developed as the decomposition of the carbonaceous
gas goes on with any uniform standard light, as, for example, the flame of an
ordinary "Carcel " burner, and arresting the operation when the illuminating power
of the carbon as thus indicated has reached the required point.
It will be readily understood that this mode involves the same general principle
as the one first described, since the uniform current employed in the last method is
a current capable of developing a uniform light of given intensity in a standard
lamp. The first method will however be found in practice the most convenient, as
when an electric lamp of standard illuminating power is used, it is not necessary
that the operator should be constantly careful to keep the current at the same
strength. It is also specially convenient for the operator to be able to compare his
work directly with a light of the same capacity and the same quality as that which
he seeks to produce.
Another mode of accomplishing the same result is to employ a galvanometer, or
some equivalent device, to indicate the resistance of the carbon during the process
of treatment as above specified, and to reduce all the conductors to a standard
resistance.
It is to be understood that the carbons are made in the first instance of as nearly
the same size as practicable, but of somewhat higher resistance than the desired
standard, and that this process of treatment corrects such unavoidable variations as
occur in carbons made according to the usual mode by, reducing them all to a definite
standard.
With conductors of equal radiating surfaces acted upon by the same current the
illuminating power of each obviously depends upon its resistance, and if they be
made of uniform resistance the conductors will be of uniform illuminating power.
As has been stated above the deposition of carbon upon the conductor during the
process of treatment increases its conductivity, and its resistance is correspondingly
diminished. Its resistance during all stages of the process will be indicated by a
galvanometer placed in the same circuit with the conductor, or arranged in any
other suitable way so as to be acted upon by the same current, it being understood
that a constant current is to be used.
The process is to be arrested when the needle of the galvanometer is brought to
a point indicating the standard resistance in the carbon.
It may be observed that several carbons may be treated simultaneously by means
of the foregoing process, with a corresponding economy in time and labor.
So far as this Invention relates to the production of conductors of standard
illuminating power, it is not to be limited to the use of a gas or vapor in a rarefied
condition, since it is obvious that the conductors may be reduced to the standard
illuminating power or standard resistance by treating them in a carbonaceous gas
at even a full atmospheric pressure, but it is believed that better results are
produced in all cases by the use of a rarefied gas, and the attenuation of the gas is
essential só far as the said Invention relates to improvement in the structure of the
carbon of which the conductor is composed.
Carbon conductors made in the modes heretofore practised, such as shaping pieces
of carbon deposit taken from the interior of gas retorts, and moulding pulverized
carbon into form under pressure, with or without other substances interinixed, or
shaping some fibrous material into the desired form and subsequently carbonizing
it, are more or less imperfect.
Those cut from the deposits of the gas retort, while in the main hard, are not of
uniform structure and are liable to develop flaws, while those produced artificially
are not only far from being uniform in structure but also are exceedingly porous.
The existence of interstices between the fibres or particles of the carbons is a
recognized clement of weakness, among other reasons because of the formation of
minute voltaic arcs across such spaces, whereby the carbon is gradually eaten away
or consumed. Another mode of preparing carbons for electric lamps has been to
deposit carbon upon some solid conductor by electrically heating it while immersed
in a gaseous or a liquid bydrocarbon at atmospheric pressure.

page_text: The difficulty practically experienced in treating the conductors by this method
is that if the temperature be carried high enough to produce a carbon deposit
otherwise of good quality the dissociation of the hydro-carbon goes on so very
rapidly that the deposition of the carbon takes place almost entirely upon the
exterior of the conductor and does not sufficiently penetrate the interstices of the
interior, and the carbon thus deposited will be comparatively soft, irregular, and
easily broken. On the other hand, if the carbon to be treated be subjected to an
intense heat in the presence of a highly attenuated carbonaceous
gas the dissociation
of such a medium will take place much more slowly than with a gas at full atmos-
pheric pressure, and the deposition will begin and will proceed the most rapidly at
the interior of the conductor, that portion being the soonest and the most highly
heated. In this manner the interstices will become filled with a fine deposit of
carbon which will firmly cement the fibres and particles of the original conductor
into a much more dense, homogeneous, and elastic mass, the exterior of which also
as the operation proceeds will be materially evened up and rounded off. For the
best results the occluded gases should be expelled from the conductor as completely.
as possible before the treatment with the carbonaceous gas begins.
The best way yet ascertained of carrying out this Invention is to place the carbon
to be treated in an exhausted receiver provided with proper electrical connections;
then pass through it a current of electricity to expel the occluded air and gases,
which when released are to be pumped from the receiver, after which admit a pure
hydro-carbon vapor or other carbonaceous gas, of a pressure equal to about one inch
of mercury, more or less, and increase the current on the conductor, carrying the
temperature up to a very high point, the time of the exposure being dependent
mainly on the thickness of the conductor and the strength of the current. By
arresting the operation at the proper point it will be found that the density of the
carbon conductor has been greatly increased, with also a large increase in its strength
and elasticity, and if desired without material change in volume; its conductivity,
although somewhat increased, still remains at a low point and its resistance
correspondingly high.
When the deposition of the carbon has been arrested if the receiver is to form the
globe of the finished lamp, the excess of gas is to be pumped out of the receiver,
which is then to be sealed up and the lamp will be ready for use. Conductors thus
prepared may also be transferred from the receiver and afterwards placed each in
its own globe enclosing a very high vacuum, or preferably a very highly attenuated
atmosphere of some carbonaceous vapor.
It will be readily understood that in working the foregoing process the higher
the attenuation of the gas used in the receiver the greater will be the temperature
required to effect the deposition of the carbon, and it is believed that the fineness
of the deposit, and thus the excellence of the product, varies in a measure as the
heat to which the conductor is subjected.
The most available gases for the purpose are the vapors of gasoline, marsh gas,
olefiant gas, or ordinary coal gas. A gas composed of nitrogen and carbon also may
be used with advantage, such as cyanogen, as derived from cyanide of mercury or
other sources. A preparation of sulphur and carbon also may be used, such as carbon
bi-sulphide.
The foregoing process, while designed primarily for the manufacture of continuous
carbons for incandescent lamps, may also be used with advantage in preparing the
carbon electrodes to be used in voltaic arc lights, as also in the preparation of
carbons to be used otherwise for electrical purposes. The Invention, again, is not
necessarily limited to the treatment in manner above described of conductors of
carbon, as conductors of other material may be greatly improved by being subjected
to the same process.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said William Robert Lake in the Great Seal Patent Office on the.
13th August 1881.
WILLIAM ROBERT LAKE, of the Firm of Haseltine, Lake, & Co., Patent Agents,
Southampton Buildings, London. "AN IMPROVED PROCESS OR METHOD OF
PREPARING CARBON AND OTHER CONDUCTORS TO BE USED FOR ELECTRIC
LIGHTING AND OTHER PURPOSES." A communication from abroad by Hiram
Stevens Maxim, of Brooklyn, New York, United States of America.
This Invention relates to the preparation of carbon or other conductors for
electric lighting apparatus, and is chiefly designed for application to that class of
such apparatus known as incandescent lamps, in which the light giving portion is a
continuous conductor of high resistance commonly formed of carbon.
The objects of the said Invention are to make such conductors of a uniform
standard illuminating power, and to make them more dense and homogeneous in
structure, and more elastic than those made by the processes heretofore in use with
a resulting increase of durability.
By the methods heretofore generally practised in making electric carbons it is
impossible to obtain any considerable number of carbons which under a current of
given intensity will develop the same light where the conductors are made of the
carbon deposit formed on the interior of gas retorts, whether by shaping such
carbon into the required form with cutting tools or by grinding it up and then
moulding it into shape under pressure, it is practically impossible to secure two
conductors having precisely the same radiating surface, or having the same
resistance. The same difficulty attends the ordinary modes of manufacturing
incandescent conductors by shaping a fibrous material into the desired form and
then carbonizing it. Differences in the superficial area of the carbons or in their
resistance will produce corresponding differences in their relative illuminating
power.
Manifestly in any system of electric lighting equality of light giving capacity in
the lamps employed is an object exceedingly desirable. The mode by which this
result may be attained, and which constitutes a part of the present Invention,
consists, generally stated, in subjecting the carbon conductor while surrounded by
an atmosphere of hydro-carbon vapor or other carbonaceous gas to the action of an
electric current in the presence of some standard light or other means for ascertaining
when the conductor conforms to the standard fixed. The intense heat generated
by the passage of the current dissociates the elements of the gas, and the carbon
set free therefrom is deposited in a state of exceedingly minute subdivision in the
pores and upon the exterior of the carbon under treatment, gradually reducing its
resistance and correspondingly changing its illuminating capacity; when this bas
been brought to the desired point, as indicated by the standard of comparison, the
operation of building up is arrested, and the finished carbon is ready to be sealed
up in the globe in which it is to be used.
The best manner heretofore discovered for regulating the extent of the change to
be effected in the resistance of electric carbons in order to produce uniformity of
illuminating power is to use a standard electric lamp, connecting it with the circuit
in the same manner as the carbon to be treated.
An apparatus suitable for this purpose is illustrated in the accompanying
Drawing, in which A, A', are the main wires of the circuit leading from the source
of, electric energy B; C is a standard lamp placed in a branch between the
main wires of the circuit, and D is a carbon to be treated, arranged in a co-ordinate

page_text: branch between the two main wires. These branches are provided with switches
of any known and suitable character. The carbon D is approximately of the same
size as that of the lamp C, but is of higher resistance, and is enclosed in a glass
receiver E whose only outlet is the tube F. Through or by means of this tube the
globe is attached to an exhausting pipe at S by any tight connection, preferably a
joint of ground glass and a mercury seal. A tube H leads to an exhausting
apparatus capable of producing a high vacuum, such, for instance, as a "Sprengel
or a "Geisler" pump; I is a vessel containing gasoline or some other very volatile
hydro carbon oil. This vessel may be filled through the tube K, which should be
hermetically sealed by a ground glass stopper or otherwise. The said vessel
· communicates with the pump through the pipes L, M, and H, and the cock N.
All of the joints and connections should be perfectly tight to prevent all ingress of
air.
The operation is as follows, that is to say:-The cock N being closed the air is
exhausted from the globe E as perfectly as possible, after which a current of electricity
may be passed through the carbon or conductor D, in order to expel from it the
occluded gases which should also be pumped from the globe. Then upon opening
the cock N the vapor of gasoline will flow from the vessel I into the globe filling
it to the required degree; practically a pressure of about an inch of mercury, more
or less, will be found sufficient. Now. inasmuch as the conductor to be treated is of
a higher resistance than the lamp, it will be found that on switching on the current
to the conductor and the lamp a smaller portion of the current will flow through
the carbon or conductor D than through the lamp C, and the light developed in it
will be correspondingly less, but as the conductor D builds up by the deposition
upon it of carbon from the surrounding gas, as above explained, its resistance
gradually falls, permitting an increased flow of the current through it, and corre-
spondingly increasing its illuminating power. When the light has become equal to
that of the standard lamp the operation is to be arrested.
Instead of arranging the standard lamp and the carbon to be treated in parallel
series in branches of the main circuit, as above described, they may be arranged in
consecutive series in the main circuit. In this case, as the entire current would be
made to pass through both the carbon D and the lamp C, the light at first developed
in the carbon will, by reason of the greater resistance of the carbon, be greater than
that of the lamp; but as the building up of the carbon by the decomposition of
the surrounding gas proceeds, with a corresponding diminution in its resistance, the
heat and the light developed by the passage of the current will gradually be
diminished until the latter is brought to the same intensity as that of the standard
limp.
According to a modification of the mode of accomplishing the above result I
subject the carbons to be treated to the action of a constant or uniform electric
current, comparing the same changing intensity of the light developed as the decom-
position of the carbonaceous gas goes on with any uniform standard light, as, for
example, the flame of an ordinary "Carcel" burner, and arresting the operation when
the illuminating power of the carbon as thus indicated has reached the required
point.
It will be readily understood that this modification of my process involves the
same general principle as the one first herein described, since the uniform current
employed in the last method is a current capable of developing a uniform light of
given intensity in a standard lamp. The first method will however be found in
practice the most convenient, as when an electric lamp of standard illuminating
power is used, it is not necessary that the operator should be constantly careful
to keep the current at the same strength; it is also specially convenient for the
operator to be able to compare his work directly with a light of the same capacity
and the same quality as that which he seeks to produce.
Another modification of my method or process of accomplishing the object of
this Invention is to employ a galvanometer, or some equivalent device, to indicate

page_text: the resistance of the carbon during the process of treatment as above specified, and
to reduce all the conductors to a standard resistance.
It is to be understood that the carbons are made in the first instance of as nearly
the same size as practicable, but of somewhat higher resistance than the desired
standard, and that this process of treatment corrects such unavoidable variations as
occur in carbons made according to the usual mode by reducing them all to a
definite standard.
With conductors of equal radiating surfaces acted upon by the same current, the
illuminating power of each obviously depends upon its resistance, and if they be
made of uniform resistance the conductors will be of uniform illuminating power.
As has been stated above the deposition of carbon upon the conductor during the
process of treatment increases its conductivity, and its resistance is correspondingly
diminished. Its resistance during all stages of the process will be indicated by a
galvanometer placed in the same circuit with the conductor, or arranged in any
other suitable manner, so as to be acted upon by the same current, it being under-
stood that a constant current is to be used.
The process is to be arrested when the needle of the galvanometer is brought to
a point indicating the standard resistance in the carbon.
It may be observed that several carbons may be treated simultaneously by means
of the process above described, with a corresponding economy in time and labor.
So far as this Invention relates to the production of conductors of standard
illuminating power, it is not to be limited to the use of a gas or vapor in a rarefied
condition, since it is obvious that the conductors may be reduced to the standard
illuminating power or standard resistance, by treating them in a carbonaceous gas
at even a full atmospheric pressure, but it is believed that better results are pro-
duced in all cases by the use of a rarefied gas, and the attenuation of the gas is
essential, so far as the said Invention relates to improvement in the structure of the
carbon of which the conductor is composed.
Carbon conductors made according to the methods heretofore practised, such as
shaping pieces of carbon deposit taken from the interior of gas retorts, and moulding
pulverized carbon into form under pressure with or without other substances.
intermixed, or shaping some fibrous material into the desired form, and consequently
carbonizing it, are more or less imperfect. Those cut from the deposits of the gas
retort while in the main hard, are not of uniform structure, and are liable to
develop flaws; while those produced artificially are not only far from being uniform
in structure, but also are exceedingly porous. The existence of interstices between
the fibres or particles of the carbons is a recognized element of weakness, among
other reasons because of the formation of minute voltaic arcs across such spaces,
whereby the carbon is gradually eaten away or consumed. Another mode of
preparing carbons for electric lamps has been to deposit carbon upon some solid
conductor by electrically heating it while immersed in a gaseous or a liquid hydro-
carbon at atmospheric pressure.
The practical difficulty experienced in treating the conductors by this method
is, that if the temperature be carried high enough to produce a carbon deposit,
otherwise of good quality, the dissociation of the hydro-carbon goes on so
very rapidly that the deposition of the carbon takes place almost entirely
upon the exterior of the conductor, and does not sufficiently penetrate the
interstices of the interior, and the carbon thus deposited will be comparatively
soft, irregular, and easily broken. On the other hand, if the carbon to be treated
be subjected to an intense heat in the presence of a highly attenuated carbonaceous
gas, the dissociation of such a medium will take place much more slowly than with
a gas at full atmospheric pressure, and the deposition will begin and will proceed
the most rapidly at the interior of the conductor, that portion being the soonest and
the most highly heated. In this manner the interstices will become filled with a
fine deposit of carbon, which will firmly cement the fibres and particles of the
original conductor into a much more dense, honogeneous, and elastic mass, the

page_text: exterior of which also, as the operation proceeds, will be materially evened up and
rounded off. For the best results the occluded cases should be expelled from the
conductor as completely as possible before the treatment with the carbonaceous gas
is commenced.
The best manner yet ascertained of carrying this Invention into practice is to
place the carbon to be treated in an exhausted receiver, provided with proper
electrical connections, then to pass through it a current of electricity, to expel the
occluded air and gases which, when released, are to be pumped from the receiver,
and then to admit a pure hydro-carbon vapor or other carbonaceous gas, of a
pressure equal to about one inch of mercury, more or less, and increase the current
on the conductor, carrying the temperature up to a very high point, the time of the
exposure being dependent mainly on the thickness of the conductor and the
strength of the current. By arresting the operation at the proper point, it will be
found that the density of the carbon conductor has been greatly increased, with
also a large increase in its strength and elasticity, and, if desired, without material
change in volume; its conductivity, although somewhat increased, still remains at
a low point, and its resistance correspondingly high.
The apparatus shewn in the Drawings may be used in the manner above explained
for the purposes of this Invention.
When the deposition of the carbon has been arrested, if the receiver is to form
the globe of the finished lamp, the excess of gas is to be pumped out of the
receiver, which is then to be sealed up and the lamp will be ready for use.
Conductors thus prepared may also be transferred from the receiver, and afterwards
placed each in its own globe, enclosing a very high vacuum, or, preferably, a very
highly attenuated atmosphere of some carbonaceous vapor.
It will be readily. understood that in working the foregoing process the higher the
attenuation of the gas used in the receiver, the greater will be the temperature
required to effect the deposition of the carbon; and it is believed that the fineness
of the deposit, and thus the excellence of the product, varies in a measure as the
heat to which the conductor is subjected.
The most available gases for the purpose are the vapors of gasoline, marsh gas,
olefiant gas, or ordinary coal gas. A. gas composed of nitrogen and carbon also
may be used with advantage, such as cyanogen, as derived from cyanide of mercury
or other sources. A preparation of sulphur and carbon also may be used, such as
carbon bi-sulphide.
The above described process, while designed primarily for the manufacture of
continuous carbons for incandescent lamps, may also be used with advantage in
preparing the carbon electrodes to be used in voltaic arc lights, as also in the
preparations of carbons to be used otherwise for electrical purposes. This Invention
is moreover not necessarily limited to the treatment in the manner above described
of conductors of carbon, as conductors of other material may be greatly improved
by being subjected to the same process.
Having thus fully described the said Invention as communicated to me by my
foreign correspondent and the manner of performing the same, I wish it understood
that I claim,
First. The above describe method of producing conductors (for electric lamps) of
uniform illuminating power, which consists in electrically heating the carbon or
other material in the presence of a carbonaceous or equivalent vapor, until by the
decomposition of such vapor they are brought to the standard power, substantially
as above set forth.
Second. The above described method of preparing conductors (for electric lamps)
which consists in subjecting them in the presence of a carbonaceous or equivalent
vapor or gas to the action of an electric current, such current being at the same
time caused to act upon a lamp of standard illuminating power or a galvanometer,
as above set forth and for the purpose specified.
Third. The above described process of preparing carbons or conductors (for electric

page_text: lamps), which consists in, first, removing the occluded gases by means of heat and
an air-pump, then subjecting the conductor to a high heat in an attenuated
atmosphere of hydro-carbon vapor or other carbonaceous gas, and afterwards
exhausting the surplus gases, substantially as above set forth.
Fourth. In the preparation of electric carbons or conductors, the cementing and
consolidation of the conductors by the deposition of pure carbon from an attenuated
atmosphere of hydro-carbon vapour or carbonaceous gas, substantially as above set
forth and for the purpose specified.
In witness whereof, I, the said William Robert Lake, have hereunto set my
hand and seal, this Thirteenth day of August, in the year of our Lord One
thousand eight hundred and eighty one.
W. ROBT. LAKE. (L.S.)