A SYSTEM OF ELECTRIC CONTACT FOR ELECTRIC CLOCKS AND FOR OTHER PURPOSES, AND PROCESS OF PURIFYING MERCURY. EMPLOYED THEREIN
Year: 1881

page_text: LETTERS PATENT to Benjamin Joseph Barnard Mills, of the Firm of Harris
and Mills, of 23, Southampton Buildings, in the County of Middlesex, Patent
Agent, for an Invention of "A SYSTEM OF ELECTRIC CONTACT FOR ELECTRIC
CLOCKS AND FOR OTHER PURPOSES, AND PROCESS OF PURIFYING MERCURY.
EMPLOYED THEREIN." A communication from abroad by Georges Leclanché,
Engineer, of Paris, in the Republic of France.
PROVISIONAL SPECIFICATION left by the said Benjamin Joseph Barnard
Mills at the Office of the Commissioners of Patents on the 25th July 1881.
BENJAMIN JOSEPH BARNARD MILLS, of the Firm of Harris and Mills, of
23, Southampton Buildings, in the County of Middlesex, Patent Agent.
"A SYSTEM OF ELECTRIC CONTACT FOR ELECTRIC CLOCKS AND FOR OTHER
PURPOSES, AND PROCESS OF PURIFYING MERCURY EMPLOYED THEREIN."
A com-
munication from abroad by Georges Leclanché, Engineer, of Paris, in the Republic
of France.
In all electric clocks, whether keyless or not, makers have recourse to electric
metallic contacts produced either in hermetically closed spaces or in the open air.
The mechanical arrangements adopted for producing these contacts are of two
kinds.
First. The contacts are produced simply by the pressure or juxta-position of the
metallic pieces destined to create said contacts, or by means of a metallic point and
a surface of mercury.
Second. The latest improvement made in the production of contact is the mixture
of two surfaces of mercury.
Contacts obtained by juxta-position inevitably cause irregularity of movement
in consequence of the variable oxidation of the pieces placed in contact.
Contacts obtained by the mixing of two surfaces of mercury obtained in a barrel
made of glass or metal absorb far too great an amount of mechanical force to be
usefully or practically applied to keyless electric clocks.

page_text: In the best clocks of this description made up to the present the system of
contact is most defective; it has the following disadvantages :-It is of single effect,
and it rapidly exhausts the batteries, as it remains permanent if the electro magnet
be not strong enough to break it at the moment of its production, and this is
infallibly the case when the pieces forming the contact become oxidized or the
batteries weakened. These defects are especially noticeable in the latest manu-
factured clocks of the above kind, in which the contacts are effected in a metallic
or other tube provided at one of its ends with a metallic point against which the
globule of mercury strikes, and as I have before said, it frequently happens that
the contact is not broken, which is a cause of stoppage and of irremediable wear.
By this new system of contact the following results are obtained :—
The contacts are multiple and successive, and are produced in a hermetically
closed space in which vacuum may be maintained, and the arrangement of the
mechanism is such that if from one cause or another the contacts should fail the
current of the battery is interrupted. The battery is thus allowed to rest and to
regain its primitive strength, which may have been diminished by polarization, over
work, or any other cause.
This system of contacts is realised by making use of one or more surfaces of
mercury.
In the Drawings annexed to the present Specification, Figure 1 relates to the
first of the two methods of putting the Invention into practice.
For this purpose is used a small glass tube A, B, having a diameter of a few
millimetres ; this tube is traversed near its interior surface and in a line parallel to
its axis by a metallic wire (platinum, for instance). This wire, which is indicated
in the Drawing by the line a, b, forms one of the poles of the battery. The other
pole of the battery is put into contact with one of the extremities of the wire of
the electro-magnet of the clock, the other extremity of the wire of the electro-
magnet being terminated by three or four points m, n, o, p, by which it enters
the tube A, B, by means of three or four metallic points destined to complete the
contact.
Before sealing this tube at both ends a meniscus of mercury m, n, is introduced
into it. This meniscus should weigh 5 to 6 grammes, or in other words, it should
be of sufficient weight to move freely by the action of gravity from one end to
the other of the small glass tube, according to the inclination given to said tube as
in the positions A, B, A", B", shown in the Drawing, which positions it occupies
when applied to a keyless clock, whose contact is produced by a partial and
alternate rotary movement.
. When the tube is in the position A¹, B¹, the meniscus m³, n', is at the end A,
when on the contrary the clockwork tends to place the tube in the position A¹¹, B",
the meniscus of mercury will occupy the extremity B of said tube.
The mercury
cannot move from A to B without passing by the points m, n, o, p, and consequently
producing four successive contacts; if these should fail the meniscus of mercury
assumes the position m", n", in which position no current can pass, and this has
the effect of preserving the battery from undue wear.
".
It is necessary to group the contacts m, n, o, p, in the vicinity of the axis x, y.
I need not add that if the battery be in proper condition the production of the
current and the mechanism of the clock tend constantly to bring the meniscus of
mercury into the position m³, n', and do not allow. of the passage of any current.
The modification of this system, as represented in Figures 2 and 3, permits.of
obtaining an electric contact between two or more surfaces of mercury, though.
only disposing of a partial circular movement and very slight mechanical power..
I have already stated at the beginning of this description that the contacts
obtained by two surfaces of mercury mingling together, said mercury being con-
tained in a barrel of glass or metal, absorb too great an amount of mechanical
power to be practically applied to keyless clocks.
In these barrels it is necessary to have a complete rotation, or at any rate a semi-
rotation, in order to make and break the contact,

page_text: By this new system of contacts the following results are obtained :-The contacts
are intimate, they may be multiplied, and they are most perfect since they are
produced between two or more surfaces of mercury. It is possible to produce
said contacts by a partial and alternate circular movement and a slightly angular
circuit, or a simple alternate oscillation is sufficient to make and break them.
The force absorbed is insignificant, and the system is applicable to all keyless
clocks.
The system may be realized in a tube of glass or metal hermetically closed,
and under all possible conditions, either in vacuum or in the presence of gas,
substances, or liquids of a disoxidizing nature, such as hydrogen, benzine, and
such like.
In order to realize this mode of contact the inventor takes, for example, a contact
of single effect between two surfaces of mercury.
A small glass tube having the form shown in Figure 2, has a cylindrical
part A, B, and a curved, part B, C, resembling the body of a retort. At the
extremity ca platinum wire p penetrates into the tube. Near the middle of
the tube at D another platinum wire p¹ penetrates into the same.
Before sealing
the said tube at A, a sufficient quantity of mercury is introduced into said tube
to fill its curved part in order to form another meniscus of mercury represented
by m', n¹.
This meniscus is free to move from one end to the other of the tube A, B, in
either direction according to the positions shown in Figure 2.
The platinum wires p and p' communicate with the electro-magnet of the clock
and with the battery. When a partial and alternate circular motion is com-
municated to the tube, the centre of which is at the intersection of the axes X, Y,
and x, y, the contacts are produced as follows:-
In the position A, B, a portion of the mercury forms a meniscus at m³, n', and
the inclination of the tube is such that the other portion of the mercury cannot
leave the curved part of the tube c.
m, n, represents the level of this mercury.
The clock being in movement, and the axis of the tube being in the position
represented by the line x, y, it tends to assume the position a¹, y'. As soon as the
meniscus m, n, has passed a horizontal position, it is induced by the action of
gravity to pass through the tube A, B, in the direction B, so as to reach the
extremity C
In the position x', y', of the tube, the mercury forms therefore one single
mass M.
The meniscus m', n', in moving through the tube passes by the platinum wire p¹
which penetrates the tube, and the quantity of mercury forming the meniscus is
sufficient to connect the said wire with the portion of mercury m, n; this portion
of mercury is not however sufficient to maintain the contact with the wire p¹ when
once the level m, n, is attained.
During this passage, if the battery be sufficiently powerful, contact is necessarily
produced, and the tube will have regained its original position x, y. If the batteries
have become too weak, the contact not being produced, the current is interrupted.
I have selected as an example a contact having a single action. It is evident
that if a multiple contact be desired (see Figure 3), it is only necessary to place
several receptacles B, C, B, C, at the under side of the tube, over which receptacles
the mercury m¹, n', will pass. Figure 3 indicates sufficiently this arrangement.
The end R is an enlargement destined to contain the mercury in case of stoppage
or failure of contact, so as to break all communication with the battery p", p¹¹¹, p.,
represent the platinum wires.
111
In order to render the working of this system perfect, a process is used which
enables the mercury to be brought to an absolute state of purity, and to introduce
it in that state into the tubes without its being affected by contact with the air,
so as to be able to produce infallibly successive electric contacts, even within the
space of a millimetre. By this process the separating surfaces are never soiled by

page_text: the least trace of oxide. This is most important, as it is well known that the
slightest trace of a foreign substance or matter may deteriorate the properties of a
metal.
What is generally considered as pure mercury, contains a certain quantity of
oxide. This quantity of oxide is almost inappreciable by weight, but it is never-
theless sufficient, under the influence of an electric spark, to give a peculiar
property to the metal, which property is most injurious to the formation of
mercurial contacts.
This mercury adheres to the glass after a series of passages of the electric spark,
and it forms a light train of mercury between the two surfaces sufficient to create a
permanent current. Or when the mercury under the same electric influence comes
into contact with a trace of oxide or oxygen in a state of dissolution, it becomes
covered with a film of oxide which prevents the metallic surfaces from uniting, so
as to form the contact or contacts.
In order to render the mercury absolutely pure, the following process is
adopted :-
From ten to fifteen grammes of pure mercury, that is to say, mercury purified
by the ordinary processes are put into a glass globe or chamber elongated at both
ends, and the same is heated up to a temperature of from 200 to 300, submitting
it to a current of purified hydrogen gas (dry); by this means is extracted all the
oxygen that may have been dissolved in the metal, as well as all trace of oxide of
mercury which is thus reduced to a metallic state. It is essential to seal the globe
at both extremities during the passage of the hydrogen gas, because if the mercury
comes into contact with the air, it absorbs a certain quantity of oxygen.
This is so important that when it is intended to fill one of the small contact
tubes according to the above description, care must be taken to previously fill said
tube with hydrogen gas.
This is easily effected by means of a jet of hydrogen gas which expels the air
from the interior of the tube.
As soon as the necessary quantity of mercury purified according to this special
process is introduced into the tube, the latter may be sealed, and it is then fit to be
used and applied to electric contact.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Benjamin Joseph Barnard Mills in the Great Seal Patent Office
on the 25th January 1882.
BENJAMIN JOSEPH BARNARD MILLS, of the Firm of Harris and Mills, of
23, Southampton Buildings, in the County of Middlesex, Patent Agent.
"A SYSTEM OF ELECTRIC CONTACT FOR ELECTRIC CLOCKS AND FOR OTHER
PURPOSES, AND PROCESS OF PURIFYING MERCURY EMPLOYED THEREIN.'
A com-
munication from abroad by Georges Leclanché, Engineer, of Paris, in the Republic
of France.
"
In all electric clocks, whether keyless or not, makers have recourse to electric
metallic contacts produced either in hermetically closed spaces or in the open air.
The mechanical arrangements adopted for producing these contacts are of two
kinds.
First. The contacts are produced simply by the pressure or juxtaposition of the
metallic pieces destined to create said contacts, or by means of a metallic point and
a surface of mercury.
Second. The latest improvement made in the production of contact is the
mixture of two surfaces of mercury.
Contacts obtained by juxtaposition inevitably cause irregularity of movement.
in consequence of the variable oxydation of the pieces placed in contact.
Contacts obtained by the mixing of two surfaces of mercury contained in
barrel made of glass or metal absorb far too great an amount of mechanical force
to be usefully or practically applied to keyless electric clocks.
In the best clocks of this description made up to the present, the system of
contact is most defective; it has the following disadvantages:-It is of single effect,
and it rapidly exhausts the batteries, as it remains permanent if the electro-magnet
be not strong enough to break it at the moment of its production, and this is
infallibly the case when the pieces forming the contact become oxydised, or the
batteries weakened.
These defects are especially noticeable in the latest manufactured clocks of the
above kind, in which the contacts are effected in a metallic or other tube provided
at one of its ends with a metallic point against which the globule of mercury
strikes, and as I have before said, it frequently happens that the contact is not
broken, which is a cause of stoppage and of irremediable wear.
By the new system of contact hereinafter described the following results are
obtained :-
The contacts are multiple and successive, and are produced in a hermetically
closed space in which vacuum may be maintained; and the arrangement of the
mechanism is such that if from one cause or another the contacts should fail the
current of the battery is interrupted. The battery is thus allowed to rest and to
regain its primitive strength, which may have been diminished by polarization,
over work, or any other cause.
This system of contacts is realised by making use of one or more surfaces of
mercury.
In the Drawings annexed to the present Specification Figure 1 relates to the
first of the two methods of putting the Invention into practice.
For this purpose is used a small glass tube A, B, having a diameter of a few
millimetres; this tube is traversed near its interior surface, and in a line parallel
to its axis by a metallic wire (platinum, for instance). This wire which is indicated
in the Drawing by the line a, b, forms one of the poles of the battery. The other

page_text: pole of the battery is put into contact with one of the extremities of the wire of
the electro-magnet of the clock, the other extremity of the wire of the electro-
magnet being terminated by three or four points m, n, o, p, by which it enters the
tube A, B, by means of three or four metallic points destined to complete the
contact.
Before sealing this tube at both ends a meniscus of mercury m, n, is introduced
into it. This meniscus should weigh five to six grammes, or in other words, it
should be of sufficient weight to move freely by the action of gravity from one end
to the other of the small glass tube according to the inclination given to said
tube, as in the positions A¹, B', A, B, shown in the Drawing, which positions it
occupies when applied to a keyless clock whose contact is produced by a partial
and alternate rotary movement.
When the tube is in the position A¹, B¹, the meniscus m¹, n¹, is at the end A,
when on the contrary the clockwork tends to place the tube in the position A", B",
the meniscus of mercury will occupy the extremity B of said tube. The mercury
cannot move from A to B without passing by the points m, n, o, p, and con-
sequently producing four successive contacts; if these should fail, the meniscus of
mercury assumes the position m", n", in which position no current can pass, and
this has the effect of preserving the battery from undue wear. It is necessary to
group the contacts m, n, o, p, in the vicinity of the axis x, y; I need not add that
if the battery be in proper condition the production of the current and the
mechanism of the clock tend constantly to bring the meniscus of mercury into the
position m¹, n¹, and do not allow of the passage of any current.
The modification of this system, as represented in Figures 2 and 3, permits of
obtaining an electric contact between two or more surfaces of mercury, though
only disposing of a partial circular movement and very slight mechanical
power.
I have already stated at the beginning of this description that the contacts
obtained by two surfaces of mercury mingling together, said mercury being contained
in a barrel of glass or metal, absorb too great an amount of mechanical power to
be practically applied to keyless clocks.
In these barrels it is necessary to have a complete rotation, or at any rate a
semi-rotation, in order to make and break the contact.
By this new system of contacts the following results are obtained :—The contacts
are intimate, they may be multiplied, and they are most perfect, since they are
--produced between-two-or-more-surfaces of mercury. It is possible to produce said
contacts by a partial and alternate circular movement and a slightly angular
circuit, or a simple alternate oscillation is sufficient to make and break them.
The force absorbed is insignificant, and the system is applicable to all keyless
clocks.
The system may be realised in a tube of glass or metal hermetically closed, and
under all possible conditions, either in vacuum or in the presence of gas,
substances or liquids of a disoxidizing nature, such as hydrogen, benzine, and such
like.
In order to realize this mode of contact the inventor takes, for example, a contact,
of single effect between two surfaces of mercury.
A small glass tube having the form shown in Figure 2 has a cylindrical part A, B,
and a curved part B, C, resembling the body of a retort. At the extremity Ca
platinum wire p penetrates into the tube; near the middle of the tube at D
another platinum wire p¹ pentrates into the same. Before sealing the said tube
at A a sufficient quantity of mercury is introduced into said tube to fill its curved
part in order to form another meniscus of mercury represented by m', n'. This
meniscus is free to move from one end to the other of the tube A, B, in either
direction, according to the positions shown in Figure 2. The platinum wires p
and communicate with the electro-magnet of the clock and with the battery.
When a partial and alternate circular motion is communicated to the tube, the

page_text: centre of which is at the intersection of the axes X, Y, and x, y, the contacts are
produced as follows :-
In the position A, B, a portion of the mercury forms a meniscus at m¹, n¹, and
the inclination of the tube is such that the other portion of the mercury cannot
leave the curved part of the tubo C. m, n, represents the level of this
mercury.
The clock being in movement and the axis of the tube being in the position
represented by the line x, y, it tends to assume the position x', y'.
As soon as the meniscus m¹, n', has passed a horizontal position, it is induced
by the action of gravity to pass through the tube A, B, in the direction B so as to
reach the extremity C₁. In the position x¹, y', of the tube the mercury forms
therefore one single mass M. The meniscus m³, n¹, in moving through the tube
passes by the platinum wire p¹, which penetrates the tube, and the quantity of
mercury forming the meniscus is sufficient to connect the said wire with the portion
of mercury m, n; this portion of mercury is not however sufficient to maintain
the contact with the wire p¹ when once the level m", n", is attained.
During this passage, if the battery be sufficiently powerful, contact is necessarily
produced, and the tube will have regained its original position x, y.
If the batteries have become too weak, the contact not being produced, the current
is interrupted.
I have selected as an example a contact having a single action. It is evident
that if a multiple contact be desired (see Figure 3), it is only necessary to place
several receptacles B, C, B, C, at the under side or the tube, over which recep-
tacles the mercury m', n¹, will pass. Figure 3 indicates sufficiently this
arrangement. The end R is an enlargement destined to contain the mercury in
case of stoppage or failure of contact so as to break all communication with the
battery. p, p, pl, represent the platinum wires.
In order to render the working of this system perfect, a process is used which
enables the mercury to be brought to an absolute state of purity, and to introduce
it in that state into the tubes without its being affected by contact with the air,
so as to be able to produce infallibly successive electric contacts, even within the
space of a millimetre. By this process the separating surfaces are never soiled by
the least trace of oxide. This is most important, as it is well known that the
slightest trace of a foreign substance or matter may deteriorate the properties of
a metal.
What is generally considered as pure mercury contains a certain quantity of
oxide. This quantity of oxide is almost inappreciable by weight, but is is never-
theless sufficient under the influence of an electric spark to give a peculiar property
to the metal, which property is most injurious to the formation of mercurial
contacts.
This mercury adheres to the glass after a series of passages of the electric spark,
and it forms a light train of mercury between the two surfaces sufficient to create
a permanent current. Or when the mercury under the same electric influence
comes into contact with a trace of oxide or oxygen in a state of dissolution, it becomes
covered with a film of oxide which prevents the metallic surfaces from uniting, so
as to form the contact or contacts.
In order to render the mercury absolutely pure, the following process is
adopted-
From ten to fifteen grammes of pure mercury, that is to say, mercury purified by
the ordinary processes, are put into a glass globe or chamber elongated at both ends,
and the same is heated up to a temperature of from 200° to 300°, submitting it to
a current of purified hydrogen gas (dry); by this means is extracted all the oxygen
that may have been dissolved in the metal, as well as all trace of oxide of mercury,
which is thus reduced to a metallic state. It is essential to seal the globe at both
extremities during the passage of the hydrogen gas, because if the mercury comes
into contact with the air it absorbs a certain quantity of oxygen. This is so
important, that when it is intended to fill one of the small contact tubes, according

page_text: to the above description, care must be taken to previously fill said tube with hydrogen
gas. This is easily effected by means of a jet of hydrogen gas which expels the air
from the interior of the tube.
As soon as the necessary quantity of mercury, purified according to this special
process, is introduced into the tube, the latter may be sealed, and it is then fit to be
used and applied to electric contacts.
Having thus described the nature of the said Invention and the mode in which
the same is carried into effect, I would have it understood that what I claim is,-
First. The application to keyless electric clocks of a series of multiple contacts in
a space hermetically closed, the arrangement of which is indicated in the above
description, the object of which is, when a meniscus of mercury is employed, to
produce the said contacts during the course of the said meniscus in a glass tube
hermetically closed, and in such manner that at the end of the said course the
mercury will be found placed so as to stop all passage of the current in case this
current should have been insufficient to again work the time piece, that is to say,
in case of stoppage of the clock.
Second. The arrangements represented at Figures 2 and 3, enabling with a
partial circular and alternate or oscillating motion to produce contacts between two
or several surfaces of mercury in a space herinetically closed. These contacts will
be made under better conditions in presence of a disoxidizing body, such as
hydrogen, benzine, and such like.
Third. The arrangement indicated at Figure 3, having for its object to produce
successive contacts between several surfaces of mercury, which has never before
been accomplished; lastly, the arrangement given to the tube, whereby all
permanent contact is broken when it has not been effective, or that the clock has
stopped.
The platinum wires can if required be changed in position, according, to the
quantity of mercury employed.
It should also be mentioned that this mode of contact is applicable to an ordinary
it can also serve to operate any kind of electric receivers.
clock;
Fourth. The application of mercury purified by hydrogen to electric contacts
generally in a space hermetically closed, deprived of atmospheric air, or containing
a disoxidizing gas.
In witness whereof, I, the said Benjamin Joseph Barnard Mills, have here-
unto set my hand and seal, this Twenty fifth day of January, in the
year of our Lord One-thousand-eight-hundred-and eighty two.