IMPROVED MEANS OF INDICATING THE DEPTH OF LIQUIDS OR SEMI-LIQUIDS IN RESERVOIRS OR OTHER RECEPTACLES, MINES, AND OTHER PLACES, SHIPS' HOLDS, SEAS, AND RIVERS
Year: 1878

page_text: LETTERS PATENT to Alexander Melville Clark, of 53, Chancery Lane, in the
County of Middlesex, Patent Agent, for the Invention of "IMPROVED MEANS
OF INDICATING THE DEPTH OF LIQUIDS OR SEMI-LIQUIDS IN RESERVOIRS OR
OTHER RECEPTACLES, MINES, AND OTHER PLACES, SHIPS' HOLDS, SEAS, AND
RIVERS." A communication from abroad by Jules Decoudun, of Paris,
France
Sealed the 13th August 1878, and dated the 25th February 1878.
PROVISIONAL SPECIFICATION left by the said Alexander Melville Clark at
the Office of the Commissioners of Patents on the 25th February 1878.
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of Middle-
sex, Patent Agent. "IMPROVED MEANS OF INDICATING THE DEPTH OF LIQUIDS
OR SEMI-LIQUIDS IN RESERVOIRS OR OTHER RECEPTACLES, MINES, AND OTHER
PLACES, SHIPS' HOLDS, SEAS, AND RIVERS." [A communication from abroad by
Jules Decoudun, of Paris, France.]
This Invention relates to improved means of indicating the depth of liquid in
reservoirs, tanks, casks, vats, cesspools, and other receptacles for liquids or semi-
liquids, and also in mines and other places, ships' holds, seas, and rivers, such indica-
tions being transmitted to any desired distance.
In order to indicate the depth of liquid in a reservoir it is usual to employ a float
with a chain and counterweight attached, passing outside the reservoir, and moving
over a graduated scale to indicate the variations in the water level. These indica-
tions however are given in inverted order, which is a disadvantage, and the
apparatus is besides uncertain in its action, subject to deterioration, and ceases to
act when ice is formed on the surface of the liquid. This means of indication is
moreover only applicable to reservoirs above ground, or in elevated positions, and
is necessarily contiguous to the reservoir itself.
According to this Invention it is proposed to indicate the height of the liquid
level in a reservoir by the pressure of the liquid itself at the bottom of the reservoir,

page_text: the indications being transmitted to any required distance from the reservoir,
whether the same be in an elevated or sunk position.
It is well known that the lowest layer of liquid in a vessel supports the weight
of the superincumbent mass, and is subjected to a pressure proportionate to the
height of the column of liquid above it, and varying with such height. Now if
beneath this layer a volume of air be confined it will support the same weight and
will be subjected to the same pressure which is proportionate to the height of the
liquid, so that by measuring this pressure by means of a manometer the height of the
liquid will be ascertained. If the gauge be removed to a distance from the reservoir
and connected with the volume of compressed air by a pipe of small diameter the
pressure of the liquid on the air confined beneath it will still be indicated by the
gauge by virtue of the law of equality of pressures of fluids.
The apparatus hereafter described attains this result, and the Invention thus
consists in principle in indicating manometrically the height of liquid or semi-liquid,
or liquid mixed with other matters in any container, by the aid of a volume of air
compressed beneath the column of liquid itself, the pressure being transmitted
through small pipes to gauges placed in any convenient positions for observation.
The combination of these three elements, viz., the air compressor, the transmitting
tube, and the manometer, as shown in Figure 1 of the Drawing, constitute the
apparatus employed in carrying this Invention into practical effect, but it will
be evident that the principle may be carried out in a variety of ways, and I will
here describe some of the means which I deem at present the most suitable for
effecting the purpose desired, while reserving the right of making any additions or
modifications which experience may suggest.
I. Compression of Air by the Column of Liquid.-If a tank, at the bottom of
which there is a chamber A open only at the lower part, be filled with liquid to the
height H, the air contained in A having no escape will be compressed by the liquid,
the pressure of the liquid being represented by the height of the column H-h. If
more liquid be added the pressure of the air confined in A will go on increasing in
proportion to the increase in the height H, while on the other hand it will be
diminished in the same proportion by lowering the liquid level. The same results
are obtained if the air chamber (which is shown of exaggerated size in Figure 2 for
the sake of assisting the explanation) be reduced to the relative dimensions shown
in Figure 3, with this difference, that the height of liquid in A will be inappreciable,
so that it may be fairly said that the pressure of the air in the chamber A accurately
represents the height of the column of liquid, and that by measuring this pressure
the height of the liquid column is ascertained.
In order to simplify the demonstration I have left out of consideration the
atmospheric pressure which would apparently effect the soundness of the theory
that the compressed air accurately represents the pressure due to the column of
liquid. Atmospheric changes do in fact exert an influence upon the surface of
the liquid in the reservoir, which will either increase or diminish the pressure of air
in the chamber A, according as the barometer rises or falls, but as will be seen the
means employed for measuring the pressure of the confined air are themselves
subject to the same atmospheric variations, and equilibrium is established, which
prevents any error from atmospheric changes.
The air vessel may be of metal, porcelain, glass, india-rubber, or other material,
according to the kind of liquid in which it is to be immersed, and it may also vary
in form and be fixed to the reservoir or separate, but sufficiently heavy to prevent
it being floated by the pressure of the air. The air vessel may be placed in the
tank, as shown at A, Figure 3, with a pipe rising from it to the top of the tank; or
the pipe may pass through the side of the tank, as at B, Figure 4, or descend
through the bottom, as at C, Figure 4; or the air vessel may be placed outside the
tank, as at D, Figure 4.
II. Conveyance of the Air Presure to the Point of Observation.-The compressed
air is conveyed through pipes of small diameter attached to the crown of the com-
pressed air vessel as by the law of the equality of pressures of fluids. The pressure of

page_text: the air in the vessel A may be transmitted through tubes to any point either in a
horizontal or vertical direction above or below the tank. By the use of suitable
gauges the pressure may be read off on the dials E, F, placed at the ends or at any
point of the pipes (see Figure 3). When the gauge is placed close to the reservoir
the length of pipe is insignificant, but when a great distance intervenes between
them the air vessel should be of larger dimensions, in order that the volume of air
in the tube should always be very much smaller than that in the air vessel.
III. Measurement of the Air Pressure; that is to say, the Height of the Liquid-
Any kind of pressure indicator may be used for ascertaining the variations in the
level of the liquid, such as columns of water or mercury, flattened and curved tubes
like that of a Bourdon gauge, india-rubber or other diaphragms, the corrugated box
of aneroid barometers, and others, and I reserve the right of adapting the one most
suited for the purpose, for which certain modifications will be necessary.
example, when using a mercury, water, alcohol, or other liquid gauge a second scale
would be required (see Figure 5), one being divided so as to represent the height of
water in feet or in metres; for example, the indication of the inetrical scale shown
in Figure 5 represents a height of 3 metres of water in the reservoir.
If mercury
For
be employed, its density being 13.6, each metre of water would be equal to 73 milli-
metres of mercury. The second scale is graduated so as to show the height of liquid
in the reservoir compared to its depth, F signifying full, and E empty, and the
fractions signifying respectively that it is a quarter, half, or three-fourths full, &c.,
according to the height of the mercury, but as the reservoirs would be of various
dimensions, and it would be impossible to provide separate gauges for each different
depth, the scale E, F, is printed upon an extensible band of india-rubber, for
example, attached to the gauge plate at E, and to a small tension screw at F, by
means of which the position of the mark F may be adjusted to correspond to the
depth of the reservoir or cistern by shortening or lengthening the scale as required.
Metallic pressure indicators may have similarly divided dials, and may also be
adapted to correspond to a reservoir of any depth by adjusting the position of the
maximuin point F of the scale by means of a screw, according to the depth of the
reservoir.
Many arrangements may be adopted; for example, in the aneroid combination
(Figure 6) the flexible corrugated box acts on a lever for working the index hand.
The pressure of the air in the aneroid box acts on the corrugated plate, and through
it on the lever, which deflects a spring whose resistance increases in proportion to
the length of the lever, and vice versa, so that by varying by means of a screw the
point at which the spring bears upon the lever the power of the gauge may be
regulated.
Many other arrangements may also be adopted, such as helical, spiral, flat, or
other springs; or the regulation may be effected by varying the leverage by means
of an external device, or the power of the springs may be modified with the same
object.
Figure 7 is a front view of the indicator represented in section in Figure 6. If
it is required to indicate the state of the reservoir without the necessity of
approaching near enough to distinguish the index hand signals would be employed,
as in Figure 8. In this case the gauge moves a disc as well as a hand, half the
surface of the disc being colored black and the other half white. This disc is
capable of making half a revolution behind a fixed dial with a semicircular aperture
in it, through which the position of the black and white disc is visible at a con-
siderable distance.
The gauge, whatever its construction, is regulated from the outside by means of
a turnscrew or key, and in applying the apparatus it is only necessary to place the
air vessel in the empty reservoir, attach the tube and gauge, which then stands at
zero or E (signifying empty), then fill the reservoir, and by means of the key make
the point F (full) of the scale correspond to the indication of the gauge. The latter
may be provided with means for automatically recording its maximum and minimum
positions.

page_text: This Invention may be employed for indicating the level of liquids, such as hot
and cold water, tar, oils, spirits, acids, &c., in reservoirs, cisterns, tanks, boilers,
vats, casks, or other vessels or containers, outside or at the top of buildings or
works, in cellars, or in other positions, the gange being placed at any distance there-
from in any convenient position above or below.
The Invention is also applicable for indicating the level of thick or semi-liquids,
or liquids mixed with other matters, such as residues of manufactures, pulp, foecal
matter in cesspools, &c., the height of water in sewers, wells, and nines, the bilge
water in ships, the height of a river, the depth of the sea, and the rise and fall of
the tide. As applied to the latter purpose may be made of sufficient size to operate
large signals in lighthouses.
For sounding in wells or elsewhere at great depths the apparatus may be com-
bined with an air chamber or bell containing a maximum gauge, hermetically
enclosed in a box, and the whole lowered to the bottom, and again raised to read
off the height of the water.
For measuring the contents of barrels and other vessels the apparatus may be
contained in a tubular rod, capable of being inserted in the barrel or other vessel.
The Invention may also be used in well-boring and other operations for ascertaining
the depth in the earth at which water is to be found. In this case the apparatus is
contained in a pointed tube with perforations to admit the water.
The indicating mechanism may also be combined with electrical apparatus for
conveying the indications to very great distances, or for giving audible signals, &c.;
and besides index hands the indicators may have pencils or other devices, and
suitable mechanisın, for tracing or marking graphically the variable height of water
at certain intervals of time.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Alexander Melville Clark in the Great Seal Patent Office on the
24th August 1878.
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of Middle-
sex, Patent Agent. "IMPROVED MEANS FOR INDICATING THE DEPTH OF LIQUIDS
OR SEMI-LIQUIDS IN RESERVOIRS OR OTHER RECEPTACLES, MINES, AND OTHER
PLACES, SHIPS' HOLDS, SEAS, AND RIVERS." A communication from abroad by
Jules Decoudun, of Paris, France.
This Invention relates to improved means of indicating the depth of liquid in
reservoirs, tanks, casks, vats, cesspools, and other receptacles for liquids or semi-
liquids, and also in mines and other places, ships' holds, seas, and rivers, such
indications being transmitted to any desired distance.
In order to indicate the depth of liquid in a reservoir it is usual to employ a
float with a chain and counterweight attached, passing outside the reservoir and
moving over a graduated scale to indicate the variations in the water level. These
indications however are given in inverted order, which is a disadvantage, and the
apparatus is besides uncertain in its action, subject to deterioration, and ceases to
act when ice is formed on the surface of the liquid. This means of indication is
moreover only applicable to reservoirs above ground or in elevated positions, and is
necessarily contiguous to the reservoir itself.
According to this Invention it is proposed to indicate the height of the liquid
level in a reservoir by the pressure of the liquid itself at the bottom of the reservoir,
the indications being transmitted. to any required distance from the reservoir,
whether the same be in an elevated or sunk position.
It is well known that the lowest layer of liquid in a vessel supports the weight
of the superincumbent mass, and is subjected to a pressure proportionate to the
height of the column of liquid above it, and varying with such height. Now if
beneath this layer a volume of air be confined it will support the same weight, and
will be subjected to the same pressure, which is proportionate to the height of the
liquid, so that by measuring this pressure by means of a manometer or gauge the
height of the liquid will be ascertained. If the gauge be removed to a distance
from the reservoir and connected with the volume of compressed air by a pipe of
small diameter, the pressure of the liquid on the air confined beneath it will
still be indicated by the gauge by virtue of the law of equality of pressures of
fluids.
The apparatus hereafter described attains this result, and the Invention therefore
consists in principle in indicating manometrically the height of liquid, or semi-
liquid, or liquid mixed with other matters in any container, by the aid of a volume
of air compressed beneath the column of liquid itself, the pressure being transmitted
through small pipes to gauges placed in any convenient position for observation.
The combination of these three elements, viz., the air compressor, the trans-
mitting tube, and the manometer, as shown in Figure 1 of the Drawing, constitutes
the apparatus employed in carrying the Invention into practical effect, but it will
be evident that the principle may be carried out in a variety of ways, and I will
here describe some of the means which I deem at present the most suitable for
effecting the purpose desired, whilst reserving the right of making any additions or
modifications which experience may suggest.
I. Compression of Air by the Column of Liquid.-If a tank, at the bottom of
which there is a chamber A open only at the lower part, be filled with liquid to
the height H, the air contained in A having no escape will be compressed by the
liquid, the pressure of the liquid being represented by the height of the column H-h.
If more liquid be added the pressure of the air confined in A will go on increasing
in proportion to the increase in the height H, while on the other hand it will be
diminished in the same proportion by lowering the liquid level. The same results

page_text: are obtained if the air chamber (which is shown of exaggerated size in Figure 2 for
the sake of assisting the explanation) be reduced to the relative dimensions shown
in Figure 3, with this difference that the height of liquid in A will be inappreciable,
so that it may be fairly said that the pressure of the air in the chamber A accurately
represents the total height of the column of liquid, and that by measuring this
pressure the height of the liquid column is ascertained.
In order to simplify the demonstration I have left out of consideration th>
atmospheric pressure, which would apparently affect the soundness of the theory
that the compressed air accurately represents the pressure due to the column of
liquid. Atmospheric changes do in fact exert an influence upon the surface of the
liquid in the reservoir, which will either increase or diminish the pressure of air in
the chamber A, according as the barometer rises or falls, but, as will be seen, the
means employed for measuring the pressure of the confined air are themselves
subject to the same atmospheric variations, and equilibrium is established, which
prevents any error from atmospheric changes.
The air vessel may be of metal, porcelain, glass, india-rubber, or other material,
according to the kind of liquid in which it is to be immersed, and it may also vary
in form, and be fixed to the reservoir or separate, but sufficiently heavy to prevent
it being floated by the pressure of the air. The air vessel may be placed in the
tank, as shewn at A, Figure 3, with a pipe rising from it to the top of the tank; or
the pipe may pass through the side of the tank, as at B, Figure 4, or descend
through the bottom, as at C, Figure 4; or the air vessel may be placed outside the
tank, as at D, Figure 4.
II. Conveyance of the Air Pressure to the Point of Observation.-The compressed
air is conveyed through pipes of small diameter attached to the crown of the com-
pressed air vessel. As by the law of the equality of pressures of fluids the pressure
of the air in the vessel A may be transmitted through tubes to any point, either in
a horizontal or vertical direction above or below the tank, the pressure may be read
off on the dials E, F, of suitable gauges placed at the ends or at any point of the
pipes (see Figure 3). When the gauge is placed close to the reservoir the length of
pipe is insignificant, but when a great distance intervenes between them the nir
vessel should be of larger dimensions, in order that the volume of air in the tube
should always be very much smaller than that in the air vessel.
III. Measurement of the Air Pressure, that is to say, the Height of Liquid.-
Any kind of pressure indicator may be used for ascertaining the variations in the
level of the liquid, such as columns of water or mercury, flattened and curved tubes
like that of a Bourdon gauge, india-rubber, or other diaphragms, the corrugated
box of aneroid barometers and others, and I reserve the right of adopting the one
most suited for the purpose, for which certain modifications will be necessary. For
example, when using a mercury, water, alcohol, or other liquid gauge, a second
scale would be required (see Figere 5), one being divided so as to represent the
height of water in feet or in meters; for example, the indication of the metrical
scale shown in Figure 5 represents a height of 3 metres of water in the reservoir.
If mercury be employed, its density being 136 each metre height of water would be
equal to 73 millimetres of mercury. The second scale is graduated so as to show
the height of liquid in the reservoir compared to its depth, F signifying full and E
empty, and the fractions signifying respectively that it is a half or three-fourths
full, &c., according to the height of the mercury, but as the reservoirs would be of*
various dimensions, and it would be impossible to provide separate gauges for each
different depth, the scale E, F, is printed on an extensible band of india-rubber, for
example, firmly attached to the gauge plate at E and to a small tension screw at F,
by means of which the position of the mark F may be adjusted to correspond to the
depth of the reservoir or cistern by shortening or lengthening the scale as required.
Metallic pressure indicators may have similarly divided dials, and may also be
adapted to correspond to a reservoir of any .depth by adjusting the position of a
the maximum point F of the scale by means of a screw, according to the depth of
the reservoir.

page_text: Many arrangements may be adopted, for example, in the aneroid combination
(Figure 6) the flexible corrugated box acts on a lever for working the index hand.
The pressure of the air in the aneroid box acts on the corrugated plate, and through
it on the lever which deflects a spring, whose resistance increases in proportion to
the
the length of the lever, and vice versa, so that by varying, by means of a screw,
point at which the spring bears upon the lever, the power of the gauge may be
regulated.
Many other arrangements may also be adopted, such as helical, spiral, flat, or
other springs, or the regulation may be effected by varying the leverage by means
of an external device, or the power of the springs may be modified with the same
object.
Figure 7 is a front view of the indicator represented in section in Figure 6.
If it is required to indicate the state of the reservoir without the necessity of
approaching near enough to distinguish the index hand, signals would be employed
as in Figure 8. In this case the gauge moves a disc as well as a hand, half the
surface of the disc being colored black and the other half white. This disc is
capable of making half a revolution behind a fixed dial with a semicircular aperture
in it, through which the position of the black and white disc is visible at a con-
siderable distance.
The gauge, whatever its construction, is regulated from the outside by means of a
turnscrew or key, and in applying the apparatus it is only necessary to place the
air vessel in the empty reservoir, attach the tube and gauge, which then stands at
zero or E (signifying empty), then fill the reservoir, and by means of the key make
the point F (full) of the scale correspond to the indication of the gauge. The
latter may be provided with means for automatically recording its maximum and
minimum positions.
This Invention may be applied for indicating the level of liquids, such as hot and
cold water, tar, oils, spirits, acids, &c., in tanks or reservoirs outside of or at the top
of buildings, the apparatus being placed either on the reservoir itself; or the gauge
may be in any convenient position at a distace therefrom or may be placed in any
part of the building so as to indicate at a glance, in the case of a boiler house for
instance, the contents of the feed water tank, and thus enable the stoker to judge
when to start or stop the pumps. The pipe communicating with the gauge may be
carried in any direction upward, downward, over walls or round corners without in
any way affecting its indications. Where the tanks are inside the building, their
contents may be indicated at one or more different parts of the same or another
building, the communication being carried if necessary through walls and across
yards, and when tanks are placed on the roofs of buildings the gauge pipes are
carried down through the different floors to the office or elsewhere, so that the
parties interested may know at a glance how much hot or cold water is at command
without the necessity of ascending to the roof for the purpose.
The Invention may also be applied for checking the contents of casks and other
vessels in which liquids are stored in cellars, the gauge being placed either on the
cask or vessel itself, or in one of the upper floors of the building.
The Invention may also be applied for indicating the depth of water in large
reservoirs, such as are often constructed of brick work on the top of an embankment,
the gauge being placed at the foot or adjacent to the pumping engine by which
the town is supplied with water.
Liquids contained in tanks or cisterns may also be similarly gauged, as well as
thick or semi-liquids, or liquids mixed with other matters, such as residues of
manufactories, malt, pulp, foecal matters in cesspools.
The height of water in sewers and wells may also be ascertained by the
apparatus, and where the well is of considerable depth the apparatus may be
combined with an air vessel, in the bottom of which is a self-registering maximum
gauge hermetically enclosed in a box, so that the apparatus which is to be attached
to a cord may be lowered slowly to the bottom of the well and then hauled up,

page_text: when the depth of water will be indicated on the gauge. The apparatus forms a
portable sounder applicable for measuring liquids of great depth.
The apparatus may also be employed for indicating to the engineman the rise of
water in mines and ships' holds, and thus enable the pumps to be set in motion at
the desired instant.
The Invention may also be applied to indicate the varying level of rivers and
streams, the rise and fall of floods and of the tide; as applied to the latter purpose
the apparatus may be placed in lighthouses, and be made of sufficient size to operate
large signals.
The apparatus may also be substituted with advantage for the glass gauges,
usually employed to indicate the contents of casks, or portable tanks, or reservoirs.
The apparatus may also when placed in the office of a manufactory serve for
controlling various operations carried on in vats, boilers, and other containers. The
apparatus is in this case applied as for a reservoir.
It is also sometimes necessary to know how much liquid is contained in a vat
beneath solid matters at its surface which prevent the liquid being seen, and in
such cases the apparatus is contained in a tubular rod, the air chamber being placed
at bottom and a gauge at top with a small pipe to connect the two. By plunging
this sounding rod into the vat, the liquid contained will be at once indicated, and
this form of apparatus may also be used to gauge the contents of casks, carboys,
and other vessels.
The apparatus may also be used for ascertaining the depth in the earth at which
water is to be found. For this purpose a pointed tube with perforations to admit
water is first driven into the ground, after which the apparatus is introduced into
the tube to show at what depth compared with that of the tube water is to be
found.
The apparatus may also be combined with electrical apparatus for conveying
the indications to very great distances or for giving audible signals, &c., and besides
index hands the indicators may be provided with suitable mechanism for tracing
or marking graphically the varying height of water at certain specified times.
Having described the nature of the Invention, and the manner of performing the
same, I declare that what I claim as the Invention to be protected by the herein-
before in part recited Letters Patent is,-
The apparatus, substantially as herein-before described and shown in the
Drawings, for indicating on a manometer or gauge the height of liquids, or semi-
liquids, or liquids mixed with other matters in any container, the said apparatus
operating by the compression of a volume of air beneath the column of liquid
itself, the pressure being conveyed through pipes to gauges placed in any convenient
position for observation, as specified.
I also claim the application of the apparatus for the various purposes mentioned.
In witness whereof, I, the said Alexander Melville Clark, have hereunto set
my hand and seal, this Twenty-third day of August, in the year of our Lord
One thousand eight hundred and seventy-eight.
A. M. CLARK.
(L.S.)