A New or Improved Mode and Means of and Instrument for Ascer- taining and Verifying the Immersion or Displacement and Draught of Steam and Sailing Ships or Vessels.
Year: 1886

page_text: Date of Application, 31st Dec., 1886
Complete Left, 29th Sept., 1887
Complete Accepted, 1st Nov., 1887
A New or Improved Mode and Means of and Instrument for Ascer-
taining and Verifying the Immersion or Displacement and
Draught of Steam and Sailing Ships or Vessels.
I THOMAS DOBIE of Elie Villa, Tighnabruaich, Argyleshiro, Engineer do hereby
declare the nature of this invention to be as follows:-
This invention comprises a new construction or arrangement of the parts, of a
tubular apparatus or instrument, and its fittings for ascertaining and verifying the
depth of water drawn by a ship, and its displacement when afloat, by the pressure of
the water within the instruments.
According to this invention a vertical vessel called the Air Chamber is placed near
the bottom of the ship, amidships, into which water through the bottom of the ship
is admitted to the lower part of the vessel by a small pipe fitted with taps or valves,
and rising in the air vessel compresses the air in the vessel with a force equal to the
immersion or depth of the ship in feet and inches below the surface of the water.
From the top of this air vessel a pipe is led to a mercurial or other pressure gauge,
preferably fitted with a tap or valve, situated in the Chart Room or other convenient
place in the ship, and the dial or index of the instrument being proportionately
marked off in feet and inches with the corresponding displacement in tons per each
inch of immersion on opposite sides of the mercury tube or index, the level of the
mercury or the index pointer will always indicate the exact immersion or draught
and displacement of the ship when afloat, on the said two scales respectively. A tube
is also attached to the air chamber within the water space, preferably fitted with a
tap also, and carried up the central bulkhead to a sufficient height above the deep
[D1

page_text: load line, and this tube being of glass and having a graduated scale attached on
opposite side of the tube indicates the actual immersion or mean draught and displace-
ment also, and the head of water in the tube acting on the air in the Air Chamber
equalizes the pressure when the ship is rolling and pitching, enabling the mean
draught being read off during any weather. Tubes might be led from the water tube
at the lower part of the air vessel to any part of the ship, and passed through the
bottom of the ship towards the bow or stern, fitted with separate taps or valves, for
taking the draught at these parts of the ship also. The actual water column gauge on
the centre of the bulkhead would always verify that indicated by the proportional
scales on the mercurial or other pressure gauge in the Chart Room or other part of
the ship; and the error due to friction in the mercury gauge being constant could
always be allowed for as say two pounds of pressure less than the real draught.
Dated this 31st day of December 1886.

page_text: A New or Improved Mode and Means of and Instrument for Ascer-
taining and Verifying the Immersion or Displacement and
Draught of Steam and Sailing Ships or Vessels.
I, THOMAS DOBIE, of Elie Villa, Tighabruaich, Argyleshire, Engineer, do hereby
declare the nature of my invention and in what manner the same is to be performed
to be particularly described and ascertained in and by the following statement in
writing, reference being had to the accompanying 2 Sheets of Drawings, and to the
letters and figures marked thereon, that is to say :-
::
This invention comprises a new construction or arrangement of the parts of a
tubular apparatus or instrument, and its fittings, for ascertaining and verifying the
depth or the mean depth of water drawn by a ship, and its displacement when afloat,
by the pressure of the water within the instrument, either by the actual level to which
it rises in the instrument, or a proportionate scale thereof which I term an
Hydrometrograph." The objects and the advantages of the invention are, to be able
at any moment by the inspection of the instrument to get the draught or mean
draught of the vessel at mid-ships, or at any part fore or aft where the instrument is
fitted, as in the main holds, Captains cabin, chart room, wheel house or other part
convenient for inspection; and thus enable the weight of cargo taken in or discharged
at any particular time to be ascertained and a record kept, and also indicate the weight
of coals taken on board or consumed during any given time; or the accumulation of
water in the holds, or ballast tanks, through defective sea cocks or other cause.
And in order that this invention and the manner of performing or carrying the
same into effect or practice may be properly understood, Two Sheets of explanatory
Drawings are hereunto appended, in which the same reference letters are used to
indicate corresponding parts in all the Figures where shown:-Figure 1 on Sheet 1
is a mid-ship section of a steam ship S showing one arrangement of the Instruments
and fittings complete, erected all in accordance with one modification of the invention,
and Figure 2 is a midship longitudinal sectional elevation corresponding to Figure 1,
both showing the instruments in elevation at right angles to each other connected to
the ordinary sea pipe c, with cocks wl, through the skin of the lower part of the ship.
The lower instrument c, d, and its index plate d³, is erected on one of the bulkheads S³,
as of the forward stockhold, for giving the actual draught of water; and the reduced
mercurial tube instrument and its index plate B B', as erected on the wall of the

page_text: chart room S³ adjacent to the midships, but it will be understood that the pressure
tube b. leading to this instrument may be carried so as to place the instrument in the
Captains Cabin, wheel-house or other convenient position of the ship desired to show
the draught or mean draught of water at midships proportionately on its scale C, it
might be in feet and inches on one scale C, and in relative weights of displacement on
the other scale D, as in tons. Figures 3 and 4 on Sheet 2 are respectively a front
elevation and a corresponding sectional plan to a large scale of the mercurial reduced
scale tube instrument BB, for erection in any convenient part of the ship.
Figure 5 shows a sectional elevation of the air and water acting chamber A'.
And
Referring to these Drawings, according to this invention a vertical close vessel,
called the air and water working chamber A, is placed near the bottom of the ship S
amidships; the outer water W, is admitted through the bottom S¹ of the ship S and
ordinary sea cocks and pipes w¹w, to the lower part of this vessel A, by a small pipe a
fitted with a tap or valve a', and the water rising in the air vessel A compresses the
air in the vessel with a pressure or force equal to the immersion or depth of the ship S
in feet and inches below the surface W of the water. From the top of this air
vessel A, a tube b, which may be fitted with a tap or valve, is led to the mercury
pressure vessel b¹ of the mercurial pressure glass tube and gauge B, B', shown in
Figures 3 and 4 on sheet 2, and as secured to the wall of the Chart Room, S³, in
Figures 1 and 2, but it may be other convenient place in the ship S. The plate B¹ of
the instrument is marked off on a mercurial scale C on one side of the mercury tube B
in feet and inches proportional to that of the actual feet and inches of the draught or
immersion of the ship to the water level W¹, at any one time. The scale shown is
divided, to indicate an immersion of from 1 to 26 feet. A scale D is shown on the
other side of the plate B1 and tube B marked off to indicate tons opposite the feet and
inches of the scale C, and is shown as marked off in hundreds of tons from 0 up to
7000 tons, and into halves of these or divisions of 50 tons. The small air tube b,
reaches to the top of the mercurial vessel 2, and the glass tube B is immersed quite
down to near the bottom in the mercury vessel b¹ so that the mercury rises in the glass
tube B proportionate to the pressure of the air in the vessel from the working
vessel A. The level of the mercury in the glass tube B will always indicate the
exact immersion or draught in feet or inches and displacement in tons of the ship
when afloat on the said two scales C and D respectively of this instrument B, B¹, in
the Chartroom S³. A second tube c is jointed to the upper part of the air chainber A,
and led down into the water space at the bottom and preferably fitted with a tap c¹
and a glass tube above and carried up and secured to a plate d' on the central
bulkhead S2 to a sufficient height above the deep load line. This tube d is of glass
and its plate has a graduated scale of actual feet and inches on one side, and a scale
of the exact corresponding tons displacement on the opposite side, so as to indicate
the actual immersion or mean draught and displacement; and the head of water in
this open tube d acting on the air in the npper part of the air Chamber A equalises
the pressure in the tube b and instrument B B' when the ship is rolling and pitching,
and thus enable the mean draught to be read off during any weather, either on the
inercurial instrument or the water tube and index d d. Other special tubes a² a
with taps a might be led from the sides of the ship or the bottom of the ship S as
indicated in dotted lines. Equivalent tubes might be led from the tube a at the
lower part of the air vessel A to any part of the ship, and passed through the bottom
of the ship towards the bow or stern, fitted with separate taps or valves, for taking
the draught at these parts of the ship also when desired. The air and water vessel Å
would preferably be fitted with a cock c³, near the bottom for cleaning the instrument
and drawing off the water when desired. The actual water column indicator d d' on
the centre of the bulkhead S2 would always verify that indicated by the proportional
scales on the mercurial or other pressure gauge B B' in the Chart room S³, or other
part of the ship; and the error due to friction in the mercury gauge being constant
could always be allowed for, as say two pounds of pressure less than the real draught,
as also the difference between the specific gravity of salt water and fresh water hy a
" constant."

page_text: 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 :-
First. The mode and means, or apparatus for ascertaining and verifying the
immersion or displacement and draught of steam and sailing ships or vessels, com-
prising an air and water pressure vessel A in the lower part of the ship connected by
tubes to two instruments, one instrument d, d', placed below the water level for
indicating the actual draught, and a second instrument &B B₁ placed in the Chart
room or other part of the ship for indicating by a proportionate scale the draught,
and on a separate scale the corresponding displacement or cargo weight, all sub-
stantially as herein described in reference to and shown in the accompanying
Drawings.
Second. The arrangement and combination of the parts of apparatus, for ascer-
taining and verifying the immersion or displacement and draught of steam and sailing
ships or vessels, comprising a pressure air and water chamber A placed near the
bottom of the ship having a tube b leading to a mercurial pressure vessel and glass
tube B, provided with separate scales C, D, for indicating the draught and corre-
sponding displacement or cargo weight, situated in the Chart room or other part of
the ship, all substantially as and for the purposes herein described, in reference to
and shown in the accompanying Drawings.
Third. In an instrument or apparatus for ascertaining or verifying the immersion
or displacement and draught of steam and sailing ships or vessels, the construction
and use of a close or pressure air and water chamber or vessel, connected below by a
tube or tubes to the outer water, and above by air tubes to a mercurial or other
reducing indicator placed in the Chart Room or other part of the ship, or by a water
tube to a water column indicator below the outer water-level, all substantially as and
for the purposes herein described, in reference to and shown in the accompanying
Drawings.