Pneumatic Tide Gauge.
Year: 1897

page_text: Pneumatic Tide Gauge.
I, ADOLF MENSING, of 99, Kurfürstenstrasse, Berlin, in the Empire of Germany,
Retired Captain, do hereby declare the nature of this inventior to be as follows;-
For the purpose of recording the alternations of tide-currents, either in the offing,
or at places where the provision of permanent water-marks is impracticable, it has
hitherto been necessary to ascertain the depth of water at the different tidal phases
by means of a "bob
or plummet, and then to compute the tidal variations from
the differences thus found.
وو
This method, for more than one reason, is apt to lead to inaccurate results; in
addition to which it is so complicated and takes up so much time, that its adoption.
has so far been restricted to but few cases.
The object of the apparatus hereinafter described is to remedy the defects attaching
to the old method, and to afford the means of reliably determining the tidal "turns
or alternations at any point or part of the sea, through the medium of automatically
operating recording apparatus erected on the sea bottom.
The improved tide gauge mainly consists of a water-tight receiver or chamber,
the interior of which, when it is lowered to the bottom of the sea, communicates
with the surrounding water, through a pipe leading from the lower part thereof.
Within this receptacle an air chamber is located, adapted to receive air under
pressure and connected with a differential pressure-gauge. The said air chamber
freely communicates with the interior of the said receiver through the medium of a
tube bent in the shape of a siphon. To the free end of this siphon-tube is con-
nected an auxiliary chamber or receiver, filled with a hygroscopic substance, say
chloride of calcium, which serves to relieve the air, as it enters the air-chamber,
from the moisture with which it is charged.
To cut off any communication between the air-chamber and the main receptacle,
the following arrangement is adopted :-
From the lowest point of the siphon there branches off a second siphon, carrying
a funnel at its upper end. Above such funnel a swinging or tilting vessel is
suspended; which vessel is filled with mercury and arranged to be tilted by the
action of clockwork at a predetermined period of time, when its contents are poured
into the siphon-tube.
In order to prevent undried air from entering the air-chamber through the siphon,
the bent portion of the same is kept permanently filled with mercury to a height or
level of about 10 centimetres.
The receiver is let down into the sea; and, in order to ensure equalization of
pressure between the interior of such receiver and the water surrounding the same,
the said receiver, before being lowered, is filled with compressed air, after which the
connection with the tube,-fitted to the lower part of the receiver and provided with
a suitable valve, is cut off. After obtaining a rise of temperature, induced by
the air-compression, the apparatus is allowed to sink down to the sea bottom, when
the tap is opened.
Should the water-pressure exceed the pressure of the air, water should be allowed

page_text: to pass into the receiver until the pressure is equalised; while in the event of the
air-pressure in the interior of the receiver being higher, the contrary effect will be
produced.
Now the moment the mercury is caused to pass from the vessel into the siphon,
by the clockwork which should be timed beforehand, the mercury will form a seal
between the air-chamber and the main receiver, rising to the same level in both
siphon-tubes, owing to the equality of the pressure prevailing in the receiver and
air chamber respectively. When, subsequently, the inner pressure becomes greater
than the outer pressure, the mercury will descend in the siphon-tube leading from
the air-chamber, while it will correspondingly rise in the other siphon-tube, and vice
versa.
The first-mentioned siphon-tube should preferably be duplicated, so that the
mercury may constantly rise or descend in the tubes of one siphon to the same extent
to which it falls or rises in the tubes of the other.
After cutting off the connection with the air-chamber, the index-hand of the
pressure gauge of the same will retain its position of rest whilst the level of the
sea continues unchanged, the weight of the water-column, supported by the tide-
gauge, then remaining constant. But whenever the weight of such water column
over the tide-gauge either increases or diminishes, the pressure-gauge hand will
turn to the right or to the left as the case may be; and this displacement of the
hand will thus directly indicate the occurring variations in the sea-level, or in
other words, the change of the tide. The tide-gauge herein described thus affords a
ready medium for determining both the time at which either high or low tide
occurs and the water-level at each of the tidal phases. And it is only necessary to
allow the Bourdon tube of the pressure-gauge to operate a style or pencil adapted
to move in contact with a revolving drum to obtain correspondingly accurate
readings.
In practice, the main receptacle should preferably be constructed in the form
of a cylindrical chamber divided into two parts or compartments. The air-
chamber may consist of a bottle or jar of steel, secured to a plate embedded in
"cardanic" rings. Upon the said plate there should, moreover, be erected (1) a
recording differential pressure-gauge; (2) a thermograph, and (3) clockwork for
tilting the mercury vessel; besides the mercury vessel should be fitted with an
auxiliary drying chamber.
In order to enable the air in the receiver to be compressed so as to make it corre-
spond to the depth to which it is sunk, a tap is provided, after which operating the
pump may be turned off. From this tap a tube should lead to the bottom of the
main receiver. When, after the apparatus has reached the sea-bottom, the said
tap is opened, pressure will thereby be equalized, and an influx or effiux of water
will accordingly take place through the said tube; by which means the accumula-
tion of an unduly large mass of water in the apparatus is obviated.
About the receiver there is placed a hoop, to which there are linked three legs
with conveniently shaped foot-plates and to which are also secured the ends of the
chain which serves to raise and lower the apparatus.
Dated this 19th dox of March 1897.
ALLISON BROS.,
Agents for the Applicant.

page_text: the same is to be performed, to be particularly described and ascertained in and by
the following statement;-
-
For the purpose of determining the range of the tides i.e. the height from low
water to high water either on the high seas or at places where beach marks cannot
be established, it has hitherto been necessary to ascertain the depth of water at
different phases of the tides by means of the lead or plummet and then to compute
the rise and fall of the tides from the differences thus found.
This method, for more than one reason, is apt to lead to inaccurate results; in
addition to this it requires the constant presence of a vessel and takes up so much
time, that its adoption has so far been restricted to but few cases.
The object of the apparatus here described is to remedy the defects attaching to
the old method, and to afford the means of reliably determining the range of the
tides at any point or part of the sea through the medium of an automatically
operating apparatus placed on the sea bottom.
Referring to the accompanying drawings:.
Fig. 1 is an elevation of the tide-gauge in position for use when lowered to the
bottom of the sea,
Fig. 2 is a plan view of Fig. 1,
Fig. 3 is a central vertical section of the apparatus showing the construction of
the tide-gauge, and
Fig. 4 is a sectional plan view on line z-z of Fig. 3,
Fig. 5 is a section at a right angle to Fig. 3.
Fig. 6 is a diagram having for its object to make the principle on which the
apparatus is based more easily understood, and in which view a detached side
elevation of the siphon a, e, and the siphon b is shown projected from and in addition
to the general diagrammatic view showing the connections of such siphons.
Referring to Fig. 6 K is a watertight casing or receiver, the interior of which,
when it is lowered to the bottom of the sea, communicates with the surrounding
water through a pipe R leading from the lower part thereof.
Within the receiver K a steel flask or air chamber L is located. It is connected
with a differential pressure-gauge M the indications on which are registered auto-
matically. The said air-chamber L communicates freely with the interior of the
said receiver K through the medium of a tube a, c bent in the shape of a siphon.
To the free end of this siphon is connected a receptacle V, filled with a hygroscopic
substance, say chloride of calcium, which serves to relieve the air, as it enters the
chamber L, from the moisture with which it is charged.
To cut off any communication between the air-chamber L and the air surrounded
by the receiver K the following arrangement is adopted From the lowest point
of the siphon a, c there branches off a second siphon b carrying a funnel at its upper
end.
Above such funnel a swinging or tilting vessel H is suspended which vessel is
filled with mercury and arranged to be tilted by the action of a clockwork at a pre-
determined period of time, when its contents are poured into the siphon tube b.
In order to prevent undried air from entering the air-chamber L through the
siphon, the bent portion of the same (b, a Fig. 6) is kept permanently filled with
mercury to a height of several centimetres which however must not stop the
tube a, c through which the air passes from V to L.
The receiver K, before lowering into the sea, is filled with air the pressure of
which is made to correspond as nearly as possible to the depth of water at the
position selected for placing the apparatus.
After this has been done the interior of the receiver K is cut off from the sur-
rounding air by a valve fitted to the tube R (Fig. 6). The air in K, being heated
through compression, suitable time must be allowed for the apparatus to acquire
the temperature of the air. It is then lowered to the bottom of the sea. The valve
closing the tube R is then opened and free communication between the interior
of the receiver K and the surrounding medium re-established. It is obvious that

page_text: by doing so the enclosed air is subjected to the hydrostatic pressure exerted by the
surrounding water and that both must be exactly the same.
Should the water be rising and the outward pressure increase thereby, more water
would enter the pipe R and accordingly the inside pressure be raised in the same
ratio.
Should the water be falling, the contrary effect would be produced.
In a similar manner the air-pressure in the air-chamber and that in the interior
of the pressure-gauge will remain absolutely the same as the hydrostatic pressure
as long as the siphon a, c is left free.
But the moment that mercury is caused to pass from the vessel H into the
funnel at the free end of the tube b, this will form a seal between the air-chamber L
and the receiver K and rise in all three tubes a, b and c to very nearly the same
level, the air-pressure being the same or very nearly the same in all.
The tilting of the vessel H is effected by the clockwork movement mentioned
above. This is set so that all the parts of the apparatus shall have acquired the
temperature of the surrounding water before the tilting takes place.
When subsequently, the pressure in the receiver K becomes less, the mercury in
the siphon-branch a will descend while it will rise correspondingly in the other
siphon tubes and c and vice versa.
The volume of air enclosed in the air-chamber L and that in the pressure-gauge M
will not be materially altered hereby as the diameter of a has been made very small
compared with the dimensions of the air-chamber L.
As moreover the air in L is free from moisture and the walls of the air-chamber as
well as the tubes are made of materials impermeable to gases and strong enough
to resist distortion by the varying pressure (not exceeding about half the atmo-
spheric pressure), the pressure exerted by the air enclosed in the air-chamber cannot
possibly suffer any alterations except by changes of temperature. As this can be
easily determined by the use of a thermograph placed in the receiver K and as the
differences between the pressures on the inside and that on the outside of the pressure-
gauge at any moment can also easily be ascertained by reference to the diagram
traced by the pencil of the self-recording pressure-gauge it is obvious that by these
means the height of the sea-level above low water at any desired moment can easily
be computed.
In practice the receiver K should preferably be constructed in the form of a
cylindrical chamber, consisting of two parts screwed together, as shown in Figs. 1
and 5. The air-chamber L may consist of a steel flask or bottle and, together
with the system of siphon-tubes, be secured to a platform (P, Figs. 3 and 5). The
latter is hung in gimbals in order to insure its horizontal position under all
circumstances.
It is also proposed to double the tube a (as shown in Figs. 3 and 4) as otherwise
the rise and fall of the mercury in this branch would be double that in the tubes b
or c, and it would consequently be necessary to make this tube very long, which
again would lead to an increase in the height of K.
Besides the air-chamber there should morcover be placed on the platform;-
1. A recording differential pressure-gauge (B, Figs. 3, 4).
2. A thermograph, (T, Figs. 3, 4).
3. The mercury vessel and the clockwork U for tilting same (Figs. 3, 4), into
such a position that the contents of such vessel when tilted can freely flow into the
open end of the tube 6 (Fig. 4), and
4. A vessel V filled with hygroscopic substance to insure the absolute dryness of
the air entering the air-chamber L through the siphon branch a, c.
In order to enable the air in the receiver to be compressed according to the depth
of the water at the position selected for placing the apparatus, a tap h (Fig. 3) is
provided, which, after operating the pump, may be turned off. From this tap h
à tube h (Fig. 3) should lead to the bottom of the main receiver. When the
apparatus has been placed on the sea-bottom, the said tap is opened, the inside
and outside pressure will be equalized thereby and an efflux of air or an influx of

page_text: water will accordingly take place through this tube. By these means the accumu-
lation of an unduly large body of water in the receiver is also obviated.
Around the receiver K there is placed a hoop Z (Fig. 1) to which there are
pivotted three legs with conveniently shaped feet, and to which are also secured
the ends of the chain which serves to raise and lower the apparatus.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what I
claim is:-
An improved pneumatic tide-gauge, characterized by a recording pressure-gauge
which is provided with a mercury trap and an air receptacle, such recording gauge
being arranged in a receptacle K whose inner air-pressure equalizes the water-
pressure surrounding the receiver which is lowered to the bottom of the sea in such
a manner that the difference between the air pressure in the chamber L and that
in the receptacle K as recorded by the pressure-gauge will directly indicate the
variations in the sea-level substantially as described and shown in the drawings.
Dated this 3rd day of December 1897.
ALLISON BROS.,
Agents for the Applicant.