Improvements in Apparatus for Measuring Electric Potential, Applicable also for Measuring Heights and for Meteorological Purposes.
Year: 1888

page_text: Date of Application, 16th Aug., 1888
Complete Specification Left, 16th May, 1889-Accepted, 10th Aug.,
1889
PROVISIONAL SPECIFICATION.
Improvements in Apparatus for Measuring Electric Potential,
Applicable also for Measuring Heights and for Meteorological
Purposes.
We ARTHUR HILL MAURICE of 37 Tudor Street, Cardiff Glamorganshire, Mineral
Surveyor, LASCELLES CARR of Tredelerch Rumney near Cardiff Newspaper Proprietor
and DANIEL OWEN of Ash Hall near Cowbridge Glamorganshire Justice of the Peace
do hereby declare the nature of this invention to be as follows:-
This invention relates to an improved method of measuring the quantity and tension,
or potential, of the static electricity posessed by any body or gas, and especially the
electric potential of the Earth, and its atmosphere, and refers principally to an
arrangement or apparatus for measuring the effects of polarization upon hermetically
enclosed fluid dielectrics when submitted to the inductive influence of an electrified
body.
It is well known that when two substances differently electrified are approached
sufficiently near to each other the dielectric, whether air, gas, or liquid, occupying
the intervening space becomes polarized, and in that state the molecules of the
dielectric assume a new and peculiar position with regard to each other.
We have discovered by experiment that when any fluid dielectric is hermetically
sealed up in a vessel and polarized by electric inductive action, as above described,
the fluid actually increases in volume, and would if free to do so, occupy more space,
but being confined it is placed under pressure, and so remains as long as the inducing
cause continues. By modifying the inductive influence so as to vary the degree of
polarization the expansion and contraction of the fluid dielectric is varied in an
exactly corresponding degree.
We measure this expansion and contraction, and varying pressure of the enclosed
dielectric with a suitable pressure gauge. The measurements given by such a gauge
are measurements of the degree of polarization of the enclosed fluid dielectric, and
they in effect represent the variations in the electric potential of any body, which,
on imparting its potential to the outside of the containing vessel, causes by inductive
influence, the polarization of the fluid dielectric within it.
(1) For the purpose of carrying our invention into effect we have constructed
various forms of apparatus. Firstly we enclose dry gas and by preference dry
atmospheric air, in a vessel made of a non-conducting substance such as glass. The
vessel is hermetically closed so that there is no communication between the air
inside and the air outside. In the interior of this vessel is placed a conducting
substance such as a thin plate of metal, or a unipolar substance such as fused sulphur
run onto a glass plate; and this interior conductor or electrode is of the same
shape as the containing vessel but of smaller size so that its outer surface is within
a short distance, say 25 inch, of the inside surface of the enclosing vessel.
The inductive action and consequent polarization takes place between the two
surfaces, the intervening dielectric (air in this case) being the polarized medium.
Any form and size of containing vessel may be used, but we find that one having
a cylindrical form, and a capacity of about 10 cubic inches is sufficient for the
purpose.
The smaller hollow cylinder or vessel placed as. an electrode within the closed
vessel must not touch the sides of the latter, and must be connected with the outside
air by a metallic rod or conducting body, such as a stout platinum wire, passing
by means of an airtight joint, through the enclosing dielectric, and terminating in
a point outside.

page_text: This is
a discharger for allowing the electric charge induced in the interior
electrode to escape, and the air to become depolarized when the inducing cause is
removed. A discharger is only required when the enclosing vessel is made of a
non-conducting substance. The air hermetically enclosed in this vessel is now
capable of being polarized by any electrified body so acting as to vary the potential
of the outside of the containing vessel, and as the degree of polarization of this
enclosed air varies with the changes of potential acting inductively from the outside
of the vessel, so there is a corresponding increase or decrease in its volume causing
a varying pressure upon the inside of the vessel.
To measure the variations of pressure we use a U shaped syphon gauge made of
glass, in which the sectional area of one limb is about 250 times greater than that of
the other. The smaller limb is open, the larger limb is closed, the upper portion
containing air and the lower portion glycerine; which fills the bend of the tube, and
stands part way up the small limb. This gauge, the small limb of which is fitted with
a scale, is placed within the air-vessel. Changes of temperature affect the air in this
gauge equally with the air enclosed in the airvessel, and have therefore no action upon
the liquid in the gauge. But when the air in the airvessel is polarized it expands,
while the air confined in the large limb of the gauge remains unpolarized, and is
compressed, the result being a fall of the liquid in the small limb of the gauge, which
may be observed through the glass side of the containing vessel.
A modified form of such a gauge as is used in an aneroid barometer, but in which
the vacuum chamber would be filled with air would be effective.
(2) Secondly we make the instrument to consist of two vessels or chambers of equal
size, both of which are two thirds filled with a liquid dielectric and one third with air,
the interior electrode and discharger before described being fitted in one of the vessels.
A glass tube passes from the centre of one vessel rising vertically to a height of say
6 inches; it is then bent back, entering the top of the second vessel and terminating
in the centre of it. Polarization of the liquid and air takes place only in the vessel in
which the electrode is fixed, and the movements of the liquid in the glass tubes, to
one of which a scale is attached, indicate the degree of polarization.
A flexible diaphragm or any other kind of pressure gauge may be introduced
between these two vessels in place of the glass tube. The two vessels as above described
need not necessarily be connected.-Each may be fitted with a vertical glass tube, the
lower ends being immersed in the liquid dielectric, and the upper ends being open to
the air. The liquid is arranged to partly fill the tubes, and it will rise and fall equally
in each for variations of temperature and barometric pressure, but in addition to
these movements the liquid in the tube connected with the vessel in which the
conducting substance is placed will vary with the degree of polarization of the fluid
dielectric contained therein. This variation is measured by a sliding scale arranged
to read only differences between the heights of the liquid in the two tubes; and the
potential of the body causing the polarization of the fluid dielectric is thus obtained.
(3) We also use an hermetically closed vessel the body of which is of a conducting
substance, and one side or face is a non-conductor such as glass, or vice versû; so that
opposite the non-conducting surface, at a distance of not more than an inch, there is
a conducting surface.
Any fluid dielectric enclosed in this vessel, acting as a medium between the two
surfaces, is subject to polarization when brought under the influence of an electrified
body acting upon it through the sides of the vessel, and a suitable pressure gauge
placed within it or otherwise connected with it would be able to indicate the degree
of polarization of the enclosed dielectric, and the potential of the body whose inductive
influence is the cause of it.
When the apparatus consists of two separate air chambers a convenient gauge may
be made by using a flexible metal diaphragm so arranged that on either side of it the
fluids in the two chambers are allowed to exert their pressure upon it; an arrange
ment of levers amplifies the movements of the diaphragin and communicates them to
an index finger observable through a glass face cemented into the gauge.

page_text: In all the above appliances the principle is the same viz.: the comparison of the
volume and consequent pressure of a fluid dielectric enclosed in a chamber where it
is subject to polarization by electric inductive influence, with the volume and pressure
of a similar fluid dielectric enclosed in a similar chamber where polarization cannot
occur; both chambers being exposed to the same temperature.
The second chamber is necessary for eliminating the error which would otherwise
result from changes of temperature.
In the second type of apparatus herein described the air-vessel may be made of a
conducting material such as metal, in which case the interior electrode must be
carefully insulated, to prevent contact between it and the sides of the containing
vessel; and no discharger would be used as it must be in the case of a non-conducting
vessel, for the fluid dielectric enclosed within it would be discharged and depolarized,
through the sides of the vessel, when the exciting cause was removed.
Assuming the process of hermetically closing the apparatus to be conducted within
an ordinary building, and under ordinary conditions as to non-insulation, the electro-
meter will be in the Earth's equi-potential surface at the time, and the fluid dielectric
enclosed within the induction chamber will posess such a degree of polarization as
At the time of
would be due to the Earth's potential whatever it might then be.
closing the apparatus it is necessary to know what the Earth's potential is so as to set
the instrument correctly with reference to the gauge. This is ascertained from a
similar and experimental electrometer, by the use of which in a long series of
observations, the Earth's mean potential-which we term zero potential has been
noted and marked on the gauge. A similar zero line is marked on the scale of the
gauge attached to each electrometer, and immediately before closing the apparatus it
is necessary to set the index finger of the gauge, or the liquid in the gauge tube
(whichever kind of gauge may be employed) in the same relative position as regards
the zero line as it is in the experimental instrument, and this is accomplished by
injecting just sufficient of the fluid used in the closed vessels into whichever of the
two may require it, to cause the gauge to give the same reading as that of the
experimental electrometer. This done the apparatus is completely and permanently
sealed up.
As long as the electrometer is kept within a building and uninsulated it is
practically a portion of the building, and merely acts as a recorder of the Earth's
varying potential at that spot. But if it be insulated it can be made to acquire and
measure the potential of any other electrified body. Or if it be placed in the open air
it will acquire and measure the potential of the atmosphere surrounding it. If placed
upon the ground it will always indicate the Earth's potential at that spot, and as this
varies at any given place directly with the attraction of gravity it follows that our
electrometer records a lower potential on higher ground where the force of gravity is
less; and in fact it affords an accurate means, not only of measuring the attractive
force of gravity but also the heights of mountains and other elevations.
By recording the variations of the Earth's potential as indicated by our electrometer
over a long period of time, and comparing the plotted diagram of this record with
meteorological phenomena, we have discovered that any increase of the Earth's
potential followed in about 21 hours time by a change in meteorological conditions,
and a fall of barometer, while any diminution in the Earth's potential is followed in
the same period by finer weather and a rise of the barometer. Our electrometer,
therefore, when hung up in a room in an ordinary building is capable of serving as a
most accurate and sensitive weather glass, affording indications of meteorological
changes nearly 24 hours before the barometer discovers any change in the density of
the atmosphere.
We do not confine ourselves to any particular size or form of apparatus or pressure
gauge, but having discovered that air, gases, and non-conducting liquids increase in
volume when polarized by electric inductive action, we claim, that by hermetically
sealing up air, or any other fluid dielectric, and so arranging that its polarization
and depolarization may be effected in the manner above described, we have devised
an apparatus capable of measuring, with the aid of a suitable pressure gauge, the

page_text: differences or variations in the electric potential of any body or bodies by allowing
the apparatus to acquire their electric potential, or by placing the apparatus in the
same equi-potential surface as the body or bodies to be tested.
Dated this Fifteenth day of August 1888.
ARTHUR H. MAURICE.
LASCELLES CARR.
DANIEL OWEN.
COMPLETE SPECIFICATION.
Improvements in Apparatus for Measuring Electric Potential,
Applicable also for Measuring Heights and for Meteorological
Purposes.
We, ARTHUR HILL MAURICE, of 37, Tudor Street, Cardiff, Glamorganshire,
Mineral Surveyor, LASCELLES CARR, of Tredelerch, Rumney, near Cardiff, News-
paper Proprietor, and DANIEL OWEN, of Ash Hill, near Cowbridge, Glamorganshire,
Justice of the Peace, do hereby declare the nature of this invention, and in what
manner the same is to be performed, to be particularly described and ascertained in
and by the following statement:-
This invention relates to an improved method of measuring the quantity and
tension, or potential, of the static electricity possessed by any body or gas, and
especially the electric potential of the earth and of its atmosphere; and refers
principally to an arrangement or apparatus for measuring the effects of polarization
upon hermetically enclosed fluid dielectrics when submitted to the inductive influence
of an electrified body.
It is well known that when two substances differently electrified, i.c., charged with
different kinds of electricity, are approached sufficiently near to each other, the
dielectric-air, gas, or liquid-occupying the intervening space becomes polarized,
and that the molecules of the dielectric assume under, and in consequence of, the
changed electric condition, a new and peculiar position with regard to each other.
We have discovered by experiment that when any fluid dielectric is hermetically
sealed up in a vessel and polarized by electric inductive action as above described, the
said fluid actually increases in volume, and would, if free to do so, occupy more space;
but inasmuch as it is confined it is subjected to pressure, and remains so as long as the
inducing cause continues. By modifying the inductive influence so as to vary the
degree of polarization, the expansion and contraction of the fluid dielectric is varied in
an exactly corresponding degree.
We measure this expansion and contraction or limit varying pressure by means of
a suitable pressure gauge. The measurements given by such a gauge are, therefore,
measurements of the degree of polarization of the enclosed fluid dielectric; and
they, in effect, represent the variations in the electric potential of any body which,
on imparting its potential to the outside of the containing vessel and its inside
electrode, causes the polarization of the enclosed fluid dielectric.
The applications of our invention are, even in the present state of the arts and
sciences, so numerous that it is practically impossible to detail them all; but we
can, and now propose to, specify what may be regarded as typical embodiments of
our invention, beginning with the most simple form of apparatus constructed
according to our invention and leading up to more complex adaptations of it. In
these several embodiments, as the same are hereinafter described and illustrated,
will be found clear explanations of the relationship between our invention on the
one hand and the methods of applying it to the various uses in the arts, to which it
is applicable, on the other.
Firstly. We enclose dry gas, and by preference dry atmospheric air, in a vessel made
of a nonconducting substance, such as glass. The vessel is hermetically closed so
that there shall not be any communication between the air inside and the air outside.
In the interior of this vessel is placed a conducting substance such as a thin plate of

page_text: metal or a unipolar substance such as fused sulphur run on to a glass plate; and
this interior conductor or electrode is of the same shape as the containing vessel
but of smaller size, so that its outer surface is within a short distance, say 25 inch,
of the inside surface of the enclosing vessel. The inductive action, and consequent
polarization, occur between the two surfaces, the intervening air being in this case
the polarized medium.
Any form and size of containing vessel may be used, but we find that one having
a cylindrical form and a capacity of about 10 cubic inches is sufficient for the purpose.
The enclosed air must be carefully desiccated. The smaller hollow cylinder or shell,
placed as an electrode within the closed vessel, must not touch the sides of the
fatter, and must be connected with the outside air by a metallic rod, or discharger,
such as a stout metallic wire passing, by means of an air-tight joint, through the
enclosing dielectric and terminating in a point outside. This is a discharger for
allowing of the charge and discharge of the interior electrode on which the polarization
and depolarization of the dielectric medium depends, and it is an essential part of the
instrument. The air hermetically closed in this vessel is now capable of being
polarized by any electrified body acting in such a way as to vary the potential of
the outside of the containing vessel, and as the degree of polarization of this enclosed
air varies with the changes of potential acting inductively from the outside of the
vessel, so is there a corresponding increase or decrease in its volume, the result
being a varying pressure upon the inside of the vessel.
To measure the variations of pressure we use a U-shaped syphon gauge made of
glass, in which the sectional area of one limb is about 250 times greater than that of
the other. The smaller limb is open, the larger limb being closed, the upper portion
containing air and the lower portion glycerine. The latter fills the bend of the tube
and stands part of the way up the small and open limb. We use glycerine because it
is non-volatile and a nonconductor; any other liquid possessing these properties
fully might of course be used. This gauge, the small limb of which is fitted with
a scale, is placed within the air vessel. Changes of temperature affect the air in this
gauge equally with the air enclosed in the air-vessel, and have therefore no action
upon the liquid in the gauge But when the air in the air-vessel is polarized, it
expands, while the air confined in the large limb of the gauge remains unpolarized
and is compressed, the result being a fall of the liquid in the small limb of the
gauge, and this fall may be observed through the glass side of the containing vessel.
A modified form of such a gauge as is used in an aneroid barometer, but in
which the vacuum chamber would be filled with air, would be effective.
Secondly. We make the instrument to consist of two vessels or chambers of equal
size. Both of these are filled two thirds with a liquid dielectric and one third with
dry air. The interior electrode with its discharge before described is fitted in one
of the vessels. A glass tube passes from the centre of one vessel rising to a height
of say 6 or 8 inches. It is then bent back entering the top of the second vessel
and terminates in the centre of it. Polarization of the liquid and air takes place
only in the vessel in which the electrode is fixed; and the movements of the liquid
in the glass tubes, to one of which a scale is attached, indicate the degree of
polarization.
A flexible diaphragm, or any other kind of pressure gauge, may be introduced
between these two vessels in place of the glass tube.
The two vessels as above described need not necessarily be connected. Each may
be fitted with a straight vertical glass tube, the lower ends being immersed in the
liquid dielectric which in this case completely fills the vessels, and the upper ends
open to the outside atmosphere. The liquid which must be non-volatile, is arranged
to partly fill the tubes, and it will rise and fall equally in each tube for variations
of temperature and harometric pressure; but, in addition to these movements, the
height of the liquid in the tube connected with the vessel in which the conducting
substance is placed, will vary with the degree of polarization of the fluid dielectric
contained therein. This variation is measured by a sliding scale arranged to
read only differences between the heights of the liquid in the two tubes, and

page_text: the potential of the body causing the polarization of the fluid dielectric is thus
obtained.
The amount of polarization, other things being equal, depends upon the area of the
electrode.
We also use an hermetically closed vessel, the body of which is of a conducting
substance and one side or face a nonconductor such as glass, or vice versú; so that
opposite the nonconducting surface, at a distance of not more than an inch, there
is a conducting surface. Any fluid dielectric enclosed in this vessel, acting as a
medium between the two surfaces, is subject to polarization when brought under
the influence of an electrified body acting upon it through the sides of the vessel,
and a suitable pressure gauge placed within it, or otherwise connected with it, would
be able to indicate the degree of polarization of the enclosed dielectric and the
potential of the body whose inductive influence is the cause of it.
When the apparatus consists of two separate air chambers, a convenient gauge
may be made by using a flexible metal diaphragm so arranged that on either side of
it the fluids in the two chambers are allowed to exert their pressure upon it. An
arrangement of levers amplifies the movements of the diaphragm, and communicates
them to an index finger observable through a glass face hermetically cemented
into the gauge.
In all the above appliances the principle is the same, viz. :—the comparison of the
volume, and consequent pressure, of a fluid dielectric enclosed in a chamber where it
is subjected to polarization by electric inductive influence, with the volume and
pressure of a similar fluid dielectric enclosed in a second chamber where polarization
cannot occur; both chambers being exposed to the same temperature.
The second chamber is necessary for obviating the error which would otherwise
arise from changes of temperature.
In the second type of apparatus herein described, the vessels may be made of a
conducting material such as metal, in which case the interior electrode must not
be in contact with the containing vessel, but is supported by insulating substances,
and the discharger must be insulated from its junction with the interior electrode
for an inch beyond the outer metallic vessel. We make the discharger and electrode
and containing vessel of the same metal. The instrument will work if different
metals are used, but in the reverse way.
Assuming the process of hermetically closing the apparatus to be conducted within
an ordinary building and under ordinary conditions as to non-insulation, the electro-
meter-i.e., the apparatus which is the subject of this invention-will be in the earth's
equi-potential surface at the time, and the fluid dielectric enclosed within the
induction chamber will possess such a degree of polarization as would be due to
the earth's potential whatever it might then be. At the time of closing the apparatus
it is necessary to know what the earth's potential is, so as to set the instrument
correctly with reference to the gauge. This is ascertained from a similar and
experimental electrometer, by the use of which in a long series of observations the
earth's mean potential has been noted and marked on the gauge.
A similar mean
potential line is marked on the scale of the gauge attached to each electrometer;
and immediately before closing the apparatus, it is necessary to set the index finger
of the gauge, or the liquid in the gauge-tube (whichever kind of gauge may be
employed), in the same relative position as regards mean line as it is in the experi-
mental instrument, and this is accomplished by injecting just sufficient of the fluid
used in the closed vessels into whichever of the two may require it to cause the
gauge to give the same reading as that of the experimental electrometer.
This done the apparatus is completely and permanently sealed up.
The range of any particular form of gauge is ascertained from actual trials.
As long as the electrometer is kept within a building and uninsulated, it is
practically a portion of the building and merely acts as a recorder of the earth's
varying potential at that spot. But if it be insulated, it can then be made to
acquire and measure the potential of any other electrified body. Or if it placed
in the open air, it will acquire and measure the electric potential of the atmosphere

page_text: surrounding it. If placed on the ground, it will always indicate the earth's potential
at that spot, and as this varies at any given place directly with the attraction
gravity, it follows that our electrometer records a lower potential on higher ground
where gravity is less; and, in fact, it affords an accurate means, not only of
measuring the attractive force of gravity, but also the heights of nountains and
other elevations.
The gauge scale for giving heights and the force of gravity is ascertained from
actual trials.
By recording the variations of the earth's potential, as indicated by our electrometer
over a long period of time, and comparing the plotted diagram of this record with
meteorological phenomena, we have discovered that any increase of the earth's
potential is followed (in from 20 to 24 hours time) by a change in meteorological
conditions, and usually by a fall of barometer; while any diminution in the earth's
potential is followed in a like period by finer weather and a rise of barometer. Our
electrometer therefore when hung up in a room in an ordinary building is capable.
of serving as a most accurate and sensitive weather glass, affording indications of
meteorological changes nearly 24 hours before the barometer discovers any change
in the density of the atmosphere.
In order that our invention, and the principles upon which the various embodiments
and applications of which it is capable are to be constructed, may be thoroughly
understood we will now describe several typical apparatus in detail, referring in so
doing to the accompanying drawings which are to be taken as part of this Specification,
and read therewith.
Referring to Fig. 1:
A is a cylindrical glass vessel hermetically closed by a vulcanite or other closing
disc a at the top. B is a hollow metal shell constituting the interior electrode. C is
the large; and the small limb of the glass pressure gauge. D is the coloured
glycerine. E is a scale behind the small limb c of the gauge. F, F are insulating
distance pieces for the purpose of holding the electrode in position. G is the
discharger passing air-tight through an insulator in the closing disc a.
The glass vessel A is filled with dry air which therefore surrounds the electrode B..
The large limb C of the gauge is also filled with dry air.
The operation of the apparatus above described is as follows. So soon as the
air within the vessel A is polarized, it expands, the degree of expansion being in
proportion to the intensity of the polarization, which will be indicated by the
depression of the glycerine in the small limb c of the gauge. The scale is marked
acccording to the particular phenomena which the instrument is designed to indicate.
The apparatus above described may be regarded as the simplest form in which our
invention can be completely embodied with due regard to utility.
Figs. 2 and 3 illustrate, by way of front and side sectional elevation, a more
elaborate embodiment of our invention than the one last described, and this is the
construction referred to in the tenth paragraph of this Specification
H and I are two glass vessels of any convenient shape. Both are filled with
glycerine for, say, about two thirds of their height, the remaining third being
occupied by dry air. I is the vessel in which the polarization takes place, inasmuch
as it is the one in which the metal electrode B is supported by insulating distance
pieces in the same way as illustrated in Fig. 1. J is a bent glass tube air tight
throughout its exposed length. The electrode B is a hollow cylindrical shell open at
each end and sparingly perforated. K is the discharger sealed into the end of its
tube k. Its limbs are of the same length and penetrate the respective vessels H
and I to the same depth below the surface of the enclosed glycerine. The glycerine
stands in each limb for about the height illustrated-taking that as representing
the level due to the earth's mean potential. The figures are drawn to scale, and
therefore indicate the relative dimensions which we find to be the best adapted for
the purpose of our invention.
Fig. 4 is a front elevation illustrating the embodiment of our invention as a
barometer

page_text: M N are two vessels of either glass or metal, each fitted with a tube m, n, of the
same bore, and filled with equal quantities of liquid. B is the electrode mounted
within the vessel N and provided with a discharger as described with reference to the
foregoing figures.
O is a thermometric scale adjacent to the tube m. It indicates a temperature
of 62°, i.e., 62° is the temperature of the room in which the apparatus is at work.
The scale on the thermometer is set out by comparing the movements of the liquid
in the tube m with a trustworthy thermometer, graduating the scale accordingly.
The liquid is set at the height representing the ascertained temperature by first
filling the tube m and then displacing the necessary quantity.
The liquid in the tube n-that from the vessel in which the polarization takes
place will, in respect of temperature, naturally stand at the same level as the liquid
in the tube m, and it is from this level as a zero that the polarization-indications
are taken.
-
P is a scale adapted to slide vertically against the tube n for the purpose of reading
off the height of the liquid in the said tube and shewing thereby the amount of
polarization taking place in the vessel N and, therefore, the potential of the earth.
This scale is divided into inches and tenths. The range of the liquid in the tube n
due to variations of potential, is found from actual trial, and the point of mean
potential is in the first instance obtained in the same way.
Zero on the scale P is adjusted to the temperature-level as indicated by the
thermometer. The height of the liquid in the tube n above this level indicates the
amount of polarization.
As the polarization (and earth-potential) increases, so the weather becomes more
rainy. This accounts for the reproduction on the scale P of the well known
weather-glass words of warning.
Figs. 5 and 6 illustrate an embodiment of our invention which in outward
appearance and also in respect of some of the mechanical devices used resembles
the well known aneroid barometer.
Qis a cylindrical metal case; and q a glass face. R is a chamber filled with dry
air only. The chamber R¹ contains dry air and also the mechanism for transferring
the movements of the flexible diaphragm r, which separates the chambers, to the
index. The diaphragm may be of corrugated metal.
R is the polarization chamber and the only purpose which is served by the
chamber R is to neutralize the expansion and contraction of the enclosed air due
to changes of temperature.
It will be noticed that the construction illustrated in Figs. 5 and 6 has no special
discharger such as is shewn in the previous figures.-With reference to this part
of our invention, viz. the provision of dischargers, we have to point out that
variations in potential could not be indicated unless the dielectric could discharge
itself. The special discharger is necessary in all cases where the enclosing vessel
being of one uniform substance (conducting or nonconducting) forms one electrode.
Where it forms both electrodes, as in the circular aneroid type, and is composed
of a conducting substance in part and a nonconductor in part, having both electrodes
in one surface, then the discharger is not necessary, because the metal electrode is
exposed to the outside air, and the glass electrode is also.
Fig. 7 is a front elevation illustrating an embodiment of our invention, according
to which the expansion of the air, within the polarizing vessel is transferred
mechanically to an index and also to a recording chart.
S, S' are a pair of vessels both full of dry air and both suspended from a beam S²
having its fulcrum at s. S' is the polarization-vessel, being fitted with an electrode
and discharger in the manner already described with reference to the foregoing
figures.
T is a glass tube terminating at each end in a vulcanite cup T1, T2. The tube and
both cups are joined air-tight to the respective vessels, and are charged with mercury,
or equivalent heavy fluid, but the latter are not full. Each cup is covered with an
elastic membrane t to prevent the mercury being spilt.

page_text: U is the recording chart actuated by clockwork in any convenient way.
V is an. index adapted to be moved by the beam over a graduated arc-shaped
scale.
The arm of the bean which carries the recording pencil is lengthened in order that
the recording trace of the pencil may be on a larger scale.
The operation of an apparatus constructed as above described is as follows:-
The expansion of the air due to polarization upsets the equilibrium of the apparatus
by displacing the mercury, and this momentary displacement is transferred to the
central index and chart by the mechanism illustrated or any other equivalent means.
Having now particularly described and ascertained the nature of our said inven-
tion, and in what manner the same is to be performed, we declare that what
we claim is,
1. The application of the expansion of an enclosed and polarized fluid dielectric to
the indication of the respective electrical conditions of the elements with which it is
contact.
2. The occlusion between two surfaces of opposite electric conditions of a fluid-
dielectric adapted to be there polarized and expanded.
3. The combination of an enclosed fluid dielectric adapted or liable to be polarized,
with devices by which the consequent expansion of the said dielectricį may be
indicated or recorded.
4. The combination with an enclosed fluid dielectric of mechanical devices adapted
to indicate its expansion when subjected to polarization, and an electric discharging
device adapted to effect depolarization.
Dated this 16th day of May 1889.
PHILLIPS & LEIGH,
No. 22, Southampton Buildings, Chancery Lane, W.C., Agents for the Applicants.