CERTAIN IMPROVEMENTS IN THE CONSTRUCTION AND OPERATION OF ROTARY ENGINES AND APPARATUS CONNECTED THEREWITH
Year: 1833

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, THOMAS
Earl of DUNDONALD, of Regent's Park, in the County of Middlesex, send
greeting.
WHEREAS His present most Excellent Majesty King William the Fourth,
by His Letters Patent under the Great Seal of Great Britain, bearing date at
Westminster, the Twentieth day of December, in the fourth year of His reign,
did, for Himself, His heirs and successors, give and grant unto me, the said
Earl of Dundonald, His especial licence, full power, sole privilege and autho-
rity, that I, the said Earl of Dundonald, my exors, admors, and assigns, or
such others as I, the said Earl of Dundonald, my exors, adñiors, or assigns,
should at any time agree with, and no others, from time to time and at all
times during the term of years therein mentioned, should and lawfully might
make, use, exercise, and vend, within England, Wales, and the Town of
Berwick-upon-Tweed, and also in all His said Majesty's Colonies and Plant-
ations abroad, my Invention of "CERTAIN IMPROVEMENTS IN THE CONSTRUCTION
AND OPERATION OF ROTARY ENGINES AND APPARATUS CONNECTED THEREWITH;" in
which said Letters Patent is contained a proviso that I, the said Earl of
Dundonald, shall cause a particular description of the nature of my said
Invention, and in what manner the same is to be performed, to be inrolled in
His said Majesty's High Court of Chancery within six calendar months next
and immediately after the date of the said in part recited Letters Patent, as
in and by the same, reference being thereunto had, will more fully and at
large appear.
NOW KNOW YE, that in compliance with the said proviso, I, the said
Earl of Dundonald, do hereby declare that the nature of my said Invention,
A

page_text: and the manner in which the same is to be performed, is described and ascer-
tained in manner following, and by the three Sheets of Drawings hereunto
annexed, that is to say:-
My said improvements in the construction and operation of rotary engines
and apparatus connected therewith, consist partly in the application of two or
three revolving pistons to rotary engines of a peculiar kind formerly invented
by me, and for which a Patent was granted to me by His present Majesty
King William the Fourth, bearing date the Eleventh day of November One
thousand eight hundred and thirty.
The said improved rotary engine is fully described in my Specification, which
was inrolled, in conformity with the said Letters Patent, on or about the
Eleventh day of May, One thousand eight hundred and thirty-one, and is
therein set forth to consist of a large hollow fixed cylinder, within which a
smaller revolving cylinder is placed excentrically, the axes or central lines of
the two cylinders being parallel to each other, but situated at such a distance
apart that the exterior circumference of the smaller revolving cylinder touches
the internal circumference of the larger fixed cylinder at one part of each of
their respective circumferences, so as to leave a lunate or crescent-shaped space
or annular channel between the two cylinders varying in its width at every
part of their circumferences like the figure of the moon in her least phase (or
most waning quarter) or like the Turkish crescent. The ends of the external
fixed cylinder are enclosed by circular plates, to which the flat ends of the
internal or excentric cylinder apply with close contact, and hollow central
projections from the said internal cylinder are received into recesses, which
are sunk into the said end plates so as to support the internal cylinder
within, and excentrically to the large external fixed cylinder, but so as to per-
mit the small cylinder to revolve about its own centre line or imaginary axis.
The revolving piston, which is to be impelled by steam or compressed air,
extends across the said lunate space or crescent-shaped channel in a direction
from the centre to the circumference of the larger cylinder, being affixed to a
revolving central axis which passes through stuffing boxes at the centres at
the end plates, and occupies the central line or axis of the larger cylinder
and which central axis is contained within the internal cavity of the small
excentric cylinder (but is not situated at the imaginary centre line thereof,)
and the edge of the extreme or outer end of the said revolving piston keeps at
all times in close contact with the interior circumference of the large fixed
cylinder, the revolving motion of the piston being concentrically with the large
cylinder, and the lateral edges of the piston also keep in close contact with the
flat ends of the said large fixed cylinder. The said piston in reaching ou

page_text: from the central axis to which it is affixed, and extending to the interior
circumference of the large cylinder, passes through an aperture in the circu:n-
ference of the smaller excentric cylinder, into which aperture it fits correctly
with a kind of compound rolling and sliding joint, which will prevent the
escape of steam through the said aperture by the side of the piston. When
the piston revolves together with its central axis around within the large
cylinder, it moves concentrically therewith, and carries the small excentric
cylinder round with it, the latter being it liberty to turn round freely, as
before stated; but in so turning round, the revolving motion of the internal
cylinder being excentric to the revolving motion of the piston, the rolling and
sliding joint in the circumferance of the internal cylinder will slide along the
piston alternately backwards and forwards to and from the central axis, when
the piston revolves and carries the internal cylinder round with it. By this
means the piston will always pass quite across the said lunate space or crescent-
shaped channel, so as to divide the same into two compartments, within one of
which a plenum is kept up by introducing steam or compressed air into it
through suitable apertures, whilst the other compartment is kept exhausted or
else kept in open communication with the atmospheric air through other suit-
able apertures, and the said steam or air, exerting an unbalanced pressure
against one side of the piston, urges it round in the lunate space or crescent-
shaped channel so as to turn the central axis of the piston round with forcible
motion which may be applied to turn or impel any kind of machinery. In
thus revolving and circulating around the said lunate space, the piston requires
to protrude more or less out beyond the circumference of the internal revolving
cylinder according to the varying width of the said lunate space; and the afore-
said rolling and sliding joint permits of such a greater or lesser protrusion of
the piston, and also permits the piston to assume as much varying obliquity of
direction in sliding through the aperture in the circumference of the small cylin-
der, as is required in order to accommodate the excentricity of the revolving motion
> of the piston to the revolving motion of the small cylinder. The two ends of
the central axis to which the piston is affixed project out each way through its
stuffing boxes at the centres of the end plates, in order to connect the axis at
either or both ends with any kind of machinery which it is intended to actuate;
And whereas my said improved rotary engine had only one revolving piston
5 circulating around within the said lunate space or crescent-shaped channel; and
as that piston could not exert an efficient power to impel machinery during
a portion of each of its revolutions, the said engine required a fly wheel to be
connected with the revolving axis of the piston, in order to regulate and keep
up the rotative motion of that piston with uniformity and continuance, or else

page_text: two such rotary engines required to be coupled together in such manner that
one engine would be exerting its full power to turn the machinery during the
period of inactivity of the other engine.
My present improvement is to apply two or three or more such revolving
pistons on the same central axis, so as to circulate round in the same lunate
space or crescent-shaped channel one after another; and the aforesaid unbalanced
pressure of steam or compressed air is caused to act upon them in succession
by beginning to impel one as soon or even sooner than it ceases to impel the
preceding piston, in order to communicate a more continual and a more uniform
exertion of forcible revolving motion to the central axis than can be done
with one piston. And when two, three, or more pistons are so applied accord-
ing to my present improvement, one of them is to be firmly affixed to the
central axis in the same manner as in my former engine; but my present addi-
tional piston (or additional pistons) must be fitted upon the said central axis
so as to be capable of moving freely upon the same through a small extent of
angular motion in respect to that piston which is affixed to the axis as well as
in respect to each other; and the several sockets by which each of the pistons
is affixed to or fitted upon the central axis are to be engrafted one into the
other, and the axis passing through all those engrafted sockets, in the same
manner as the knuckles or jointed parts of a door hinge are put together, and
the pistons resemble the flat leaves of such a hinge. Each of the several
pistons must pass through an aperture in the circumference of the small excen-
tric cylinder, those apertures being disposed at equal distances from each other
around that circumference, and each piston must be fitted correctly into such
aperture, with the same kind of compound rolling and sliding joint to make a
steam-tight fitting, as is described in my former Specification, (but which was
there described as applied only to that one piston which is affixed to the central
axis,) in order that the said rolling and sliding joints, conjointly with the liberty
of motion upon the central axis which is allowed to my present additional
piston or pistons as aforesaid, will permit of all those varying obliquities of
direction which each of the said pistons is required to assume in sliding through
its aperture in the circumference of the small excentric cylinder during the
révolution of the several pistons one after another around their lunate space
or crescent-shaped channel. And note, the forcible revolving motion which is
exerted by the steam or compressed air against my present additional piston
(or additional pistons), and which, as before mentioned, are fitted freely upon
the central axis, (so as to have no hold thereon to turn the same,) is trans-
mitted to the central axis through the medium of the small interal and excen-
tric cylinder, which latter, being urged round by one or other of my said addi-

page_text: tional pistons, will in turn urge round that piston which is affixed to the central
axis, so as to actuate the same with all the forcible revolving motion which is
excited by all the several pistons.
And for the more complete explanation of this part of my said improvements
I have hereunto annexed a Drawing, wherein Figure 1 is a transverse vertical
section, and Figure 2 a longitudinal vertical section, of an improved rotary
engine, with two revolving pistons, according to my present improvement.
A, A, is the large fixed cylinder, which may be supported on feet a, a. E, E,
is the internal revolving cylinder, and e, e, are its hollow central projections
upon which it is supported within but excentrically to the large cylinder A, A.
D is the central axis passing through stuffing boxes d, d, at the centres of the
end plates B, B, and occupying part of the central cavity within the internal
cylinder E, E; and C is that revolving piston which is affixed to the axis D.
B, B, are the circular end plates fixed by screw bolts b, b, to the flanges which
project around the circumference of the large cylinder A, A. Those end plates
close the end of the large cylinder, and include the ends of the small revolving
cylinder E, E, and also the lateral edges of the revolving pistons between the
flat surface of the said end plates; and recesses f,f, are sunk into the end plates
excentrically to their stuffing boxes d, d, to receive the hollow central projec-
tions e, e, of the internal cylinder E, E, and about which projections the latter
revolves concentrically to itself, but excentrically to the large cylinder and to
the piston, as before mentioned. 4, 4, is the rolling and sliding joint by which
the piston C is fitted into its aperture through the circumference of the internal
cylinder, and which joint permits the piston to assume any varying obliquity
of direction in the said aperture which is requisite to accommodate to the
excentricity of the internal cylinder as that cylinder and the piston revolve
together; but the said rolling and sliding joint always prevents any escape of
steam through the said aperture by the side of the piston. I, 1, is a metallic
packing plate, which is applied into a recess in the circumference of the large
cylinder, so as to range exactly with that part of the said circumference
where the internal cylinder touches the same; and stuffings of hemp or cotton
may be applied behind the said plate e, e, to cause it to press with gentle con-
tact against the circumference of the internal cylinder E, E, so as to preserve
a steam-tight joint between the two terminations of the lunate space or crescent-
shaped channel, in order to separate that portion thereof in which there is to be
a plenum from that other portion which is to be exhausted or left open to the
atmosphere. The edges of the piston are provided with similar metallic pack-
ing plates, which may also have stuffing behind them to keep them in contact
with the interior circumference of the large cylinder A, A, and with the flat

page_text: surfaces of the end plates B, B, so as to prevent the escape of steam by the
edges of the piston. x, x, and z, z, are circular packing rings, which are lodged
in circular grooves excavated in the circular end plates B, B, and which may
have stuffings applied behind them to press them in contact with the ends of
the internal revolving cylinder E, E, so as to prevent escape of steam.
The parts above described are nearly the same as those of my former
engine. My present improvements are, the additional piston X, which is
fitted upon the central axis D by a central socket, part 10, through which
the axis passes; and the central socket, part w, of the piston C, which is
affixed to the axis D, is cut away, in order that it may engraft with the
part 10 in the manner of the knuckles of a hinge. The additional piston X
is at liberty to move upon the axis D, through a small extent of angular motion
in respect of the piston C; and the aperture in the circumference of the internal
cylinder E, through which it passes, is provided with a rolling and sliding joint
12, 12, of a similar construction to that marked 4, 4, and before described.
The entrace passage G and exit passage I are adapted for the passage of the
steam or compressed air, by which the pistons are to be propelled with con-
tinuous circular motion in the direction indicated by the arrow; and the
continuations of those passages beyond the orifices which are represented in
Figure 1, being canied through an ordinary four-way cock, the said passages
can, by turning that cock, be made to change their respective characters, so
that I will become the entrance, and G the exit passage, in which case the
pistons will be impelled round in a contrary direction to that indicated by
the arrow, in order to reverse the direction of the motion of the machinery
which the engine is intended to actuate; and, by closing the said four-way
cock, the passages can be entirely cut off, in order to stop the engine; also, by
closing the cock partially, the speed of the motion of the engine may be
regulated at pleasure.
The operation of the said rotary engine, according to my present improve-
ment, is as follows:-Steam or compressed air being admitted through the
entrance passage G, will pass along the cavity 2, 2, into one of the narrow
extremities of the lunate space, and, by filling that extremity, will act beneath
the piston C. The other corresponding narrow extremity of that lunate space
is exhausted or open to the atmosphere by its communication through the
cavity 3, 3, with the eduction passage I; and that part of the lunate space
which is included between the two pistons C and X is at present filled with the
steam which has just completed its office of impelling the piston X round into
the piston represented in the Figure; but the piston X is in the act of passing
beyond the commencement of the cavity 3, 3, and after so passing it will then

page_text: allow the said steam to escape instantaneously by the eduction passage I. This
escape will take place at the same moment that the other piston C has passed
beyond the termination of the cavity 2, 2, and then any further entrance of
steam before the piston C will be prevented; but all the steam which does
enter will act behind the piston C, which will be subjected to an unbalanced
pressure in consequence of the said pressure of incoming steam behind it, and
the said escape of the outgoing steam from before it, and by that unbalanced
pressure it will be impelled round in the lunate space, turning the central
axis D, together with the machinery which the same is to actuate. My addi-
tional piston X is carried round at the same time in consequence of the turning
motion which is given to the small excentric cylinder, but without producing
any effect, whilst it is passing over the packing plate e, which is at the place
where the contact of the external and internal cylinders takes place, and which
contact forms the division between the two terminations of the lunate space.
This passive inactivity of the motion of my additional piston X continues until
the same has arrived at the position in which the piston C is represented in
Figure 1, at which time the said piston C will have arrived at the position in
which X is there represented; and the period of active exertion of the piston C
being then concluded, that of the other piston X will then begin by an action
of the steam exactly the same as that before stated in respect to the com-
mencement of the action of the piston C and the active operation of the
piston X being so begun will continue to turn the central axis D during
all the time whilst the other pin C is passing through its period of inactive
motion; wherefore, by the duplication of the pistons of my former improved
rotary engine (which duplication is one of my present improvements), a con-
tinual action will be kept up to turn the axis D with forcible motion.
And whereas the extent of surface which each of the revolving pistons of
such a rotary engine exposes to the unbalanced pressure which occasions
their motion is continually varying whilst they are turning round; and
according as they occupy different parts of the lunate space or crescent-
shaped channel, the forcible motion which will be exerted by two pistons
when combined in one engine, according to my present improvement, as
herein-before described, although continual, will not be uniformly forcible;
for the same will be less forcible at the time when one piston is relieved by
the other, from the performance of the active duty, than it will be at
the middle part of the period of active performance of one piston, because
the latter then occupies the widest part of the lunate space. Wherefore,
a further part of my present improvements is to apply and combine three
revolving pistons in the same engine, as is represented in Figure 3, Sheet 1,

page_text: to circulate round in the same lunate space or crescent-shaped channel, in
order to give forcible motion to the same centre axis D, upon which they
are all three mounted; one revolving piston, marked C, being affixed
thereto, as in my former Specification; and the other two pistons, marked
X and Y, being fitted thereon, with liberty of motion about the axis D,
through a small extent of turning motion by each of those two pistons, inde-
pendently of the other piston; and each of the three revolving pistons being
fitted through a rolling and sliding joint, applied in the aperture which is
made through the circumference of the internal revolving cylinder E, E, for
the piston to pass through, in order that it may protrude beyond their circum-
ference quite across the lunate space to the circumference of the large cylinder
A, A. The said three apertures and joints must be disposed at exactly equal
distances around the circumference of the internal excentric cylinder E, E.
The operation of the three combined pistons, and the manner whereby one
relieves the other, and takes its place in the performance of the active duty, is
nearly the same as above described, that a repetition is unnecessary, the only
difference being that before any one piston has ceased to operate with a small
but increasing force, beginning nearly as soon as the force created by its
predecessor begins to diminish, owing to the latter having passed beyond the
widest part of the lunate space; wherefore, the decreasing force with which
each piston must finish the latter half of its active performance is in a great
measure compensated by the decreasing force with which the succeeding piston
at the same time begins the first half of its active performance.
Another part of my present Improvement in the Construction and Operation
of Rotary Engines is represented in Figures 4 and 5, of Sheet I., and consists
in the application of folding or jointed flap pistons to revolve or circulate
around within a lunate space or crescent-shaped channel, which is constructed
according to my said former Patent; namely, a large exterior hollow cylinder,
containing within it a smaller cylinder, which is situated so much excentrically
to the larger one that the circumferences of the two cylinders will form con-
tact one part of each of these circumferences. A, A, is the large exterior, and
B, B, are its end plates. It is caused to revolve round about the internal
excentric cylinder by the action of the steam or compressed air by which the
engine is to be worked. E, E, is the internal cylinder, which is immoveably
fixed by means of cylindrical projections D, D, extending out from each end of
it; and the two extremities of those projections are solidly fixed to the
supporting standards a, a. The cylindrical parts of the projections D, D, of
the internal cylinder are excentrical to the circumference E, E, thereof; and
the end plates B, B, are fitted on the said cylindrical parts D, so as to be at

page_text: liberty to revolve around the same; and the motion of the large cylinder A in
so revolving will be concentrical to its own circumference. e, e, is a packing
plate applied into a recess at the most excentrical part of the convex circum-
ference of the internal fixed cylinder E, E, where the external revolving cylinder
touches the same; and stuffing may be applied behind the plate e, e, to press
it gently in contact with the interior concave circumference of the external
revolving cylinder A, A, in order to form a division between the two extremi-
ties of the lunate space, and separate that portion thereof in which there is to
be a plenum from that other portion which is to be exhausted or left open to
the atmosphere. 2, 2, are circular rings applied in grooves which are formed
around the flat ends of the internal fixed cylinder E, E, and they may have
stuffing behind them to press them gently in contact with the end plates B, B,
of the exterior revolving cylinder A, A, so as to prevent the escape of steam
between them. C1 and C2 are two flap pistons which are lodged in suitable
recesses formed in the circumference of the external revolving cylinder A, A,
and they are united thereto by joints c, c, at one extremity of each flap piston,
so as to fold or be moveable about those joints, in the same manner as doors
are moveable upon their hinges, and by such folding motion about their joints
the said flap pistons will apply their other edges which are farthest from
their joints c to the convex circumference of the internal fixed cylinder E, E,
so as to reach quite across the lunate space or crescent-shaped channel, in
order to divide the same into distinct compartments, and steam or compressed
air being introduced into one of those compartments (through the entrance
pipe or passage G), whilst the other compartment is exhausted or is left open
to the atmospheric air (through the exit pipe or passage I, I,) there will be an
unbalanced pressure acting against one side of that flap piston which reaches
across the lunate space and divides it into compartments as aforesaid, and that
action will tend to turn the exterior cylinder A, A, round with a continuous
rotary engine. For the said flap pistons come into operation in succession
alternately, in the same manner as herein-before described respecting Figure 1,
so that one piston will be acting efficiently whilst the other is passing through
the inactive portion of its revolution; and during that inactive period the last-
mentioned piston will be turned about its joints c, so as to retire into its recess
in the circumference of the external revolving cylinder A, A, in which position
the surface of the flap piston will come to correspond precisely with the interior
surface of the large cylinder A, A, in the manner shewn at C 4, and then
the retired piston can pass by the packing plate e, e, without permitting the
escape of steam by the same at the time when the piston is so passing in like
manner as the escape is prevented at other times. The entrance passage G, by

page_text: which steam or compressed air is introduced, passes through one end of the
fixed cylindrically-formed part D, by a suitable pipe which is jointed thereto,
and the passage turns outwards to the circumference of the internal cylinder
E, E, as shewn by dotted lines in Figure 5. The exit passage I is similar.
The forcible motion or power which will be exerted by the engine may be
communicated to any kind of machinery which it is intended to actuate by
means of a circular ring of teeth affixed to the outside of the external
revolving cylinder A, A, or affixed to one of the side plates B, as is represented
at N, Figure 4, those teeth being adapted to gear or work into the teeth of
other toothed wheelwork in a suitable manner for the transmission of the
motion and power from the cylinder A, A, to the machinery. And if it is
required to render such an engine capable of turning round in either direction,
then two other flap pistons C3 and C4 may be applied so as to turn about
their joints c, c, in a contrary direction to the two first-mentioned flap pistons,
C1 and C2; therefore the external cylinder A, A, will be provided with two pairs
of flap pistions C1, C2, and C 3, C 4; but one of those pairs must be kept
secured within their respective recesses by applying suitable means. of fastening
from the outside of the cylinder A, so as to take firin hold of those pistons in
order to retain them in the situations shewn at C3, C4. The other pair, C.I,
C 2, being left at liberty to move about their joints c, c, in which case the
engine will be impelled round in the direction of the arrow, Figure 5, by the
action of unbalanced pressure, before described; but when it is required to
reverse the direction of the motion of the engine, the pair of flap pistons C 1,
C 2, must be retained and made fast within their respective recesses, and the
other pair, C3, C4, must be set at liberty. The operation of the latter to
receive the action of unbalanced pressure, and cause the external cylinder
A, A, to revolve, will then be exactly the same as before described, but the motion
will take place in a reversed direction. And in order that one pair of the said
folding pistons may be detained in their respective recesses, and the other pair
set free, as before described, with promptitude and facility, so as to prepare the
engine for working in a contrary direction, the joints c, c, of the several pistons
may each have a short axis projecting out from it, and passing through a
suitable socket in the end plate B to the outside thereof, and lever arms may
be fixed on the extreme ends of all the said projecting axes to serve as external
lever handles, by which the folding motion of the pistons within can be com-
manded or restrained. And the handle at the extremity of each of the said
ever arms being moved outwards from the centre of the end plate B, will
fold that piston to which it belongs into its recess; and the piston may be kept
therein by retaining the said handle in its outward position by means of any

page_text: uitable latch or catch or bolt, which may be applied to the end plate B in the
anner of a door latch or lock. And the said latches or locks for the handles
f the said pairs of pistons being let loose at the same time that the handles
f the other pair are so detained as aforesaid, the engine will be prepared for
vorking in a reverse direction. And note, the kind of rotary engine last
lescribed may be constructed with the external cylinder A, A, immovably
ixed, and the internal excentric cylinder E, E, may be caused to revolve
within it by the aforesaid action of steam or compressed air by unbalanced
pressure against a pair of flap valves, in which case those flap valves should be
applied to the small internal cylinder, with suitable recesses for their reception;
and the packing plates e, e, should be applied in a suitable recess in the concave
circumference of the large cylinder A, A; but an engine so constructed will
not be capable of having the direction of its motion reversed. And in either
mode of constructing such a rotary engine, my present improvement in respect
thereto is confined to the use of a lunate space or crescent-shaped channel for
such flap valves to circulate and act in, in the manner herein-before explained;
but whereas rotary engines with flap valves to circulate within circular and
curved chambers of various forms have been long known, I make no claim
thereto unless such flap valves are applied to circulate within a lunate space
or crescent-shaped channel, which is formed as aforesaid, and as is set forth in
my said former Specification, by applying a smaller internal cylinder excentri-
cally within a larger cylinder, the circumferences of the two being in contact
at one part of each circumference respectively. And note, by way of variation
in the proportioning of such lunate space the concave circumference of the
small internal excentric cylinder may, if thought proper, be made to intersect
the concave circumference of the larger exterior cylinder, so as to protrude out
beyond that concave circumference into a suitable recess, which may be pro-
vided at one part of the external cylinder, in order to receive such protrusion;
and packing plates similar to those marked d, d, may be then applied at one or
both of the places in the concave circumference of the larger cylinder where
the same is intersected by the protrusion of the concave circumference of the
smaller cylinder. And in all cases (excepting in those which require the
exterior cylinder to revolve, as represented in Figures 4 and 5,) such variation
in the proportioning of the lunate space (by causing the concave circumference
of the small internal excentric cylinder to intersect instead of merely to touch
the concave circumference of the larger cylinder) will not affect the properties
or mode of operation of such a lunate space, or be any departure from the
principle of my said improvements.
My Improvements in the construction and operation of rotary engines

page_text: as herein-before set forth are equally adapted to those rotary steam
engines which are actuated by low-pressure steam, with condensation thereof
to obtain an exhaustion, or by high-pressure steam which is allowed to
escape into the open air after having performed its intended office. Or rotary
engines, constructed and operating according to my said improvements, may
be actuated by compressed air or other elastic fluids, or by pressure of water
or other non-elastic fluids. Or otherwise, such rotary engines being suitably
proportioned, and turned round with forcible motion derived from any adequate
first-moving power, may be used for the elevating or the exhausting or the
compressing of fluids after the manner of pumps, instead of being used as a
first-moving engine to impel other machinery. Or rotary engines, constructed
and operated according to my said improvements, may be used as a meter of
such fluids; for when it is turned round by a stream or current of the fluid, it
will form a measure of the quantity thereof which has passed through the
engine, because a certain determinate quantity must pass for every revolution
which is made; and the revolving part of the engine being connected to suitable
wheelwork provided with dials and indexes or pointers of the kind which are
used in clocks or watches, the same will record and indicate the number of
revolutions which the revolving part of the engine has made since it was set to
work, or since the dials were last observed; and thence, knowing the actual
quantity of fluid which must pass through the engine at each revolution, the
whole quantity which has passed since it was set to work or last observed may
be known. The proportions and dimensions of the parts of rotary engines
which are constructed according to my said improvements as herein-before set
forth, as well as the materials which are to be used in so constructing, must
be varied in order to adapt the engine for the particular use for which it
is intended, whether to be acted upon and impelled by elastic or non-
elastic fluids, in order to exert forcible motion for the purposes of a first
mover, or whether it is to be itself impelled with forcible motion derived from
some other first-moving machine for any of the purposes for which pumps are
usually employed. All which variations and adaptations will be familiar to
competent practical engineers who have made themselves fully acquainted with
the nature of my invention, as herein-before set forth; and hence it is scarcely
necessary to remark that non-elastic fluids require larger apertures for passages
than elastic fluids, and that the moveable fittings of the pistons may be packed
with leather in lieu of metallic packings when cold water is to pass through
the engine. The cavities which join to the apertures for the entrance and exit
of the fluids may be made in the flat surface of the end plates, and will pro-
duce the same effect as if they were made in the interior concave surface of

page_text: the exterior cylinder, as herein-before described; but in all cases the said
cavities must terminate at such places that one of the compartments into which
the lunate space is divided by that piston which is in active operation must be
filling (or be full) whilst another of the said compartments is emptying or
empty. And when such rotary engines are to be used for steam or acruform
fluids, and oil or grease is required for lubricating all the moving parts, the
same may be introduced into the hollow cavity of the internal cylinder,
and from thence the oil or grease will flow to supply all the moving parts.
And as to that part of my present improvements which relates to apparatus
connected with rotary engines, the same consists in certain apparatus to be
used on board ship at sea for the purpose of compressing and exhausting air
by force which is derived from the rolling motion and alternating agitation of
the ship or vessel in a heaving or troubled sea, in order to actuate or impel
rotary engines by exerting an unbalanced pressure within the same by the air
which has been so compressed and exhausted, and thus obtain forcible motion
or mechanical power for useful purposes on board ship. The said apparatus
is adapted to contain fluid quicksilver or mercury in various receptacles which
are to be fixed on board ship at a distance apart from each other, as, for
instance, at the opposite or larboard and starboard sides of the vessel, and the
lowest parts of the said opposite receptacles communicate freely with each other
through suitable pipes or channels which extend athwart-ship across the vessel.
And in navigating the great oceans, where a strong swell or agitation of the sur-
face of the sea commonly prevails, and occasions the vessel to roll alternately lar-
board and starboard with an incessant oscillating motion, the mercury contained
in my said apparatus is caused to flow, in consequence of its own gravity, out of
one of the said receptacles, which becomes elevated by the rolling motion of
the vessel, through the said communicating pipe, athwart-ship into the opposite
receptacle, which is depressed by the same cause. And the entrance of the
mercury into the last-mentioned or depressed receptacle is rendered operative
upon air previously contained in that receptacle to compress that air, and
then expel it in a compressed state through suitable communications and
valves into another suitable receptacle or air container, which is provided for
retaining the compressed air, and which container is connected by a pipe and
suitable regulating cock or valve with the entrance passage to the rotary
engine in such manner that the said air container will bear the same relation
to that engine as the boiler does to a steam engine; viz, it is the source from
which the compressed elastic fluid is supplied to cause that plenum in a suit-
able compartment of the engine by which its piston is impelled. And, at the
same time, the departure of the mercury from the first-mentioned or elevated

page_text: receptacle will occasion an exhaustion or rarefaction therein, whereby air may
be inhaled or drawn into it, through suitable communications and valves, out
of another suitable receptacle or air receiver, which is provided in order to
be thus exhausted, and which is connected by a suitable pipe with the eduction
passage of the rotary engine in such manner that the said exhausted receiver
will bear the same relation to that engine as the condenser does to a steam
engine; viz, it is a vacuity which is prepared by exhaustion to receive the elastic
fluid, which has performed its office of producing a plenum in the engine, and
which requires to be drawn out from a suitable compartment in the engine in
order to exhaust the same. And it is by so exhausting one compartment in
the engine whilst a plenum is occasioned, as before explained, within another
neighbouring compartment thereof, that the moveable piston which forms the
separation between the said two compartments is subjected to and unbalanced
pressure, and is thereby impelled with the forcible motion which the engine is
intended to exert and communicate to other machinery. And as soon as the
rolling motion of the vessel causes a reversal of the operation above described,
that receptacle for mercury which was recently elevated by the rolling motion
begins to descend, and that receptacle which was depressed begins to ascend
again, whereby the same mercury will begin to flow back again through the
communicating pipe athwart-ship, by its own gravitation, quitting that
receptacle into which it had before entered, as above described, and returning
into that which it had before quitted; and that returning flow of mercury is
caused to produce a repetition of the same action as before described, but with
a reciprocally contrary relation in respect to each of the aforesaid receptacles
for mercury, but with a similar relation in respect to the air container and air
receptacle aforesaid; that is to say, the mercury, in returning into that
receptacle out of which it flowed at the preceding time above described, will
compress that air which was inhaled as aforesaid by exhaustion into that
receptacle during such flowing out, and the mercury will then expel that air
in a compressed state, through suitable communications and valves, into the
same air container before mentioned, from which the plenum of the rotary
engine is to be supplied; also at the same time the returning departure of
the mercury from that receptacle into which it flowed at the preceding time
occasions an exhaustion therein, and a consequent inhaling of air, through suit-
able communications and valves, out of the same air receiver before mentioned,
which is provided for the purpose of exhausting the engine. Wherefore, in all
cases of elevation of one of the said receptacles for mercury, and the depression
of the opposite one, in consequence of the rolling motion of the vessel, whether it
be to the larboard or to the starboard, the forcible compression of air into the

page_text: aforesaid air container, and the exhaustion of air from the aforesaid air
receiver, will take place simultaneously, and will enable a rotary engine or
engines to be worked on board ship with a power which is derived from the
agitation of the sea, and which will be greater as that agitation is more
violent. And the rotary engines which I prefer for such purpose may be
constructed according to my aforesaid improvements in the construction and
operation of rotary engines, but any other kind of rotary engines may be
used for the same purpose, including those which produce rotary motion by
means of a crank or cranks from a piston or pistons moving backwards and
forwards within straight cylinders in the manner most commonly practised in
marine steam engines. Or the aforesaid effect of my said apparatus may be
produced by a more direct action of the mercury than herein-before described,
without the intervention of air, by applying a suitable rotary engine, to be
turned by the gravitating force of the mercury itself when it flows through the
aforesaid pipes or channels, which extend athwart-ship from the receptacle
for mercury at one side of the vessel to that on the opposite side. The said
pipes or channels being suitably arranged and provided with such communi-
cations and valves, that the influx of mercury into such rotary engine, and the
exit thereof from the same, will always take place in the same directions
respectively, whether the flow of mercury athwart-ship by which such influx
and exit is occasioned proceeds from larboard to starboard or from starboard
to larboard. And the forcible rotary motion which is derived from a rotary
engine or from rotary engines, when the same are worked on board ship by the
operation of my said apparatus connected therewith, may be applied to turn
paddle wheels for propelling the vessel through the water, or to work her
chain or other pumps for clearing out leakage water or for extinguishing
fire, or to turn the capstan or windlass or any other revolving machinery
which can be applied in abatement of or in aid of the manual labour of the
crew and the performance of their duties. And respecting the arrangement
combination of the parts of such an apparatus to be connected with rotary
engines for the aforesaid purpose, the same must depend (as well as the
dimensions and proportions of those parts) upon the kind of vessel on board
of which the apparatus is to be applied, and the kind of machinery which
is intended to be actuated by the power of the rotary engine, which is to be
worked by aid of such apparatus, whether paddle wheels, or pumps, or capstan
or other machinery, all which circumstances vary so much that the arrange-
ment, combination, dimensions, and proportions of parts must be left to the
discretion and judgment of the engineer who undertakes to fit any particular
ship or vessel with such an apparatus, whereof the principle and mode of

page_text: action being fully understood by him, he can have no difficulty in executing
the same by the aid and judicious application of the knowledge current
amongst those who are in the habit of constructing steam engines for maritime
purposes.
And for the more complete explanation of the mode of action of my said
apparatus, I have given a representation of the same in Sheets II. and III.,
wherein A, A, Figure 6, represents a transverse midship section of a ship
or vessel with my said apparatus fixed on board the same, and connected with
a rotary engine a. B, B, is a strong transverse beam to support the apparatus;
c, c, are the receptacles for the mercury; and D, D, the communicating pipe
or channel which proceeds athwart-ship from the lower part of one recep-
tacle B to the lower part of the other; E, E, are the air receivers which are
to be exhausted by the inhaling of air into the receptacle C, C; whenever
the mercury flows out from them the air as inhaled is drawn out of the
receiver E through valves a, a, which open downwards, and F is the eduction
pipe of the rotary engine x which proceeds therefrom to join to the
receivers E, E; G, G, are the air containers which communicate with the
receptacles C, C, by tubes b, b, and valves c, c, which open upwards and
admit the compressed air which is expelled from the receptacle C, C, when
the mercury flows into them; H, H, is the supply pipe to the engine
proceeding from the air containers G, G, to the induction passage of the
engine. It is no way necessary that the air receivers E and containers G
should be placed over the receptacles C for the mercury, as represented
in the Figure (which is only drawn for explanation); the said air vessels
may be placed by the sides of the mercury vessels, or they may be placed
close to the engine, in which case the pipes F and H will join immediately
to the receptacles for mercury with the valves a, a, and b, b, at their respec-
tive junctions, and the other ends of the same pipes F and H will be
joined to the air receivers E, E, and air containers G, G, respectively, or
in that case one vessel of adequate capacity will answer the same purpose
as the two vessels G, G, and another vessel will answer for the two vessels E, E,
or in fact the eduction pipe F being made of adequate capacity will serve
in place of both the air receivers E, E, and a large supply pipe F will serve
for the two containers G, G. L, L, is the revolving axis of the rotary engine,
which may be prolonged across the vessel beyond her sides to carry paddle
wheels at its two extremities, or it may be applied by toothed wheel-work
to actuate other machinery. The receptacles C, C, being each half filled
with mercury, and the pipe D, D, being quite filled as denoted by the yellow
color, each oscillation of the vessel will cause the contained mercury to run

page_text: through D out of one receptacle C into the other, until one becomes quite
empty, and the other quite full; that one which is emptying of mercury will
inhale air from one or other of the receivers E, E, so as to exhaust the same;
and the other receptacle which is filling with mercury will compress and
expell air from it in a compressed state into its corresponding containers G, G;
and as soon as the vessel begins to oscillate in an opposite direction the contained
mercury will begin to run back again through D out of that receptacle C,
which is full, into the opposite one, which is empty; and by the action of the
valves a, a, and b, the inhaling of air by that receptacle which is emptying
of mercury will still act to exhaust from the engine through the eduction
pipe F, whilst the expulsion of air from that receptacle C which is filling
with mercury will still act to compress air for the supply of the engine_through
the pipe H. A suitable sluice cock may be provided on the communicating
pipe or channel D, D, to close the same entirely or partially when it is
required to suspend or moderate the action of the said apparatus.
And it may be observed that the operation of my said apparatus by deriving
force from the rolling motion of the vessel will not tend to increase that rolling;
but, on the contrary, all the force which is so obtained will act as a resistance
to the rolling, and will diminish the same. And it may also be remarked that
the rolling motion of a vessel in a heavy sea is not altogether occasioned
by motion of the vessel in the water, but consists in great part of a swelling
motion of the water in which the vessel partakes; for as the surface of the sea
runs in a continual succession of inclining waves or swells, the vessel has a
natural tendency to settle herself to suit the surface, and thereby to incline
first one way and then the other, just as the surface of the water changes
its inclination, the gravitating tendency of the mercury in my said apparatus
will tend to keep the motion of the vessel in conformity with the said motion
of the water, and thereby to prevent those desultory surges and motion of the
vessel in the water which occasions the greatest severity of strain upon
a vessel when labouring in a troubled or broken sea. And note, although
I have herein-before spoken of my receptacles for mercury as being placed
on opposite sides of the vessel, larboard and starboard, they may be placed
one towards the stem and the other towards the stern of the vessel, with their
communicating pipe D running fore and aft, in which case my apparatus
5 will derive its force from the pitching motion of the vessel at the head and
stern, instead of the rolling motion. Or otherwise one receptacle may be
placed forward towards the stern on the larboard side, and the other fellow
receptacle on the starboard side towards the stern, with their communicating
B

page_text: pipe D running obliquely or diagonally athwart-ship, in which case my
apparatus will derive force from both the pitching and the rolling, whether
those motions are combined or separate. And in order that the appa-
ratus may make a correct equipoise on board the vessel, two such pairs of
receptacles may be applied, so as to have two receptacles exactly opposite to
each other on the larboard and starboard sides, although they are connected
diagonally by their communicating pipes D, which will cross each other with
contrary obliquities. And in all cases, to avoid an inconvenient magni-
tude in the receptacles for mercury, several distinct pairs may be used, each
pair having its own communicating pipe D, whether it is disposed athwart-
ship, or fore and aft, or diagonally; and although every such pair of receptacles
may be made to act in concert to exhaust from and compress into the same
air receivers and containers, yet each communicating pipe D having its own
sluice or regulating stopcock, any pair may, by closing that cock, be thrown
out of action whilst the others are kept working, by which means the power
which is exerted by the whole apparatus may be adapted to the existing
circumstances. The receptacles for the mercury and other communicating
pipe D must be made of iron, and in order to diminish the expence of the
mercury it may be amalgamated with us much lead or tin as it will contain
without materially impairing its fluidity.
Sheet III. represents a section Figure 10, and a plan Figure 9, of such an
apparatus for the compression and exhaustion of air, and working a rotary
engine thereby, in the manner last described. G is the large air container for
supplying the engine, placed amidship close to the rotary engine, and commu-
nicating with its induction passage; the compressed air is forced into the
container G through any of the supplying pipes H, H, H, II, and their valves,
from any two of the four mercurial receptacles C, C, C, C, which happen to be
depressed at the time by the rolling motion; and E is the air receiver, which is
also placed midship, and connected with the eduction passage of the rotary engine
x; and the air is exhausted from it through any of the pipes F, F, F, F, by the
inhaling action of any two of the four mercurial receptacles C, C, C, C, which
happen to be elevated at the time by the rolling motion. And note, as my said
apparatus always operates upon the same mass of included air for alternately com-
pressing and exhausting the same by the gravitating action of the same mass of
mercury which is shut up along with the said air, it is obvious that any elastic gas
may be substituted for common air if there should be any advantage in such
substitution; and whether air or gas be so used a great quantity thereof may be
forcibly injected by suitable pumps, so as to overfill the apparatus therewith in

page_text: a state of greater compression and elasticity than the atmospheric air previous to
setting the apparatus to work; and such air or gas may be always retained under
such compression within my said apparatus during the operation thereof. Or in
lieu of air or other elastic fluid water or other suitable non-elastic fluid may be
included and shut up with the mercury, so as to fill my said apparatus, in order
to transmit the forcible motion which is derived from the motion of the
mercury to the rotary engine, in the same manner as has been herein-before
described to be done with air or elastic fluid, the passages and other parts
of rotary engine being in such case suitably proportioned for being actuated
by the non-elastic fluid as herein-before stated.
Figure 7, Sheet II., explains the mode of working a rotary engine by
a direct action of the mercury as herein-before mentioned. The rotary
engine x, x, may be constructed in a similar manner to Figure 3, Sheet I.,
but with four revolving pistons instead of three; the communicating pipe D, D,
between the two receptacles C, C, for the mercury joins to the rotary engine
at each side thereof, so that one portion of the pipe D serves for the induction,
and the other portion for the eduction; pipes and valves are applied at each
end of the pipe D where it joins to each of the two receptacles C, in order
to permit the mercury to flow in one direction, but to prevent it returning
in an opposite direction. Wherefore when the vessel inclines so as to cause
the mercury to run in that direction, the current of mercury passing through
the engine will cause its revolving pistons to turn round, and then at the
returning vibration of the vessel the return of the mercury through the same
passage D, D, will be prevented by the valve a, b, but the mercury will be
permitted to return through another communicating pipe E, E, which has
also its valves at c and d, opening in an opposite direction to the valves a, b,
of the pipe D, and each portion of the pipe E is connected with the engine
by the same entrance and exit passages as the two portions of the pipe D,
but the connections are reversed, that is to say, the portion of the pipe E
which joins to either receptacle, also joins to that passage of the engine at
the opposite side thereof to that side on which the said receptacle is situated;
wherefore by this mode of cross connecting the pipe E with the engine, the
mercury will be caused to pass through the engine in the same direction
when returning through the pipe E as it did when proceeding through the
pipe D. f,f, in the same Figure, denotes an air pipe, which may be applied
for the purpose of compressing air by the motion of the mercury, in the
manner herein-before described, in addition to its direct action on the rotary
engine. Or in lieu of constructing a rotary engine for receiving the direct

page_text: action of the mercury in the manner represented in Figure 7, it may be con-
structed to operate on the principle of a breast water wheel, but enclosed within
a suitable iron case; the rotary engine must have radiating blades affixed to and
propecting out from a cylindrical drum which is mounted upon an axis, the outer
edges of the said blades being packed with leather to cause them to fit close to
the flat sides, and to the concave breasting of the case within which the drum
is inclosed, so that the mercury being poured upon the said radiating blades of
the drum above the said breasting will act thereon by its weight to turn the drum
with rotary motion, and in this case one portion of each of the communicating
pipes D and E between the receptacles for mercury must convey
the mercury
from these receptacles into an elevated receptacle in the middle of the vessel
situated higher up above the keel thereof than the ordinary receptacles c, c; and
from that elevated receptacle the mercury is to flow upon the radiating blade of
the rotary engine in the same manner as water flows from a mill dam upon
the floats of a breast wheel, and the mercury having so flowed down the
circular breasting and turned the engine, will then pass into another recep-
tacle situated lower or nearer to the keel of the vessel, and that lower
receptacle being connected by the other portions of the pipes D and E, and
their valves a and b, with the receptacles c, c, the mercury will be conveyed
back into one or other of them whenever by the rolling they descend; and
having so received the mercury, they will, when the return of the rolling
causes them to ascend, again pour out the same mercury through the other
portions of the pipes D and E, and their valves a and b, into the more
elevated receptacle from which the mercury is to flow upon the radiating
blades of the rotary engine as aforesaid.
Having now described my said improvements, and the manner of carrying
the same into effect, I, the said Thomas Earl of Dundonald, do hereby declare
that the Invention whereof the exclusive use is granted to me by the said
Letters Patent consists in the application of two, three, or more revolving
pistons to such rotary engines as operate with a lunate space formed by
including a small cylinder within a large cylinder (and the circumferences
of the two touching or intersecting each other at one place) so as to leave
a crescent-shaped channel for such pistons to circulate in, instead of using
only one piston according to my former Invention, in order by such increase
in the number of the said revolving pistons to obtain a more continuous and
uniform exertion of mechanical power, in the manner herein-before set forth;
also in the apparatus connected with rotary engines for the purpose of applying
the graviating force, which mercury or other ponderous fluid will exert on

page_text: board ship in an agitated sea, and for transmitting that force to impel rotary
engines in the manner herein-before fully set forth.
In witness whereof, I, the said Thomas Earl of Dundonald, have here-
unto set my hand and seal, this Twentieth day of June, One thousand
eight hundred and thirty-four.
Inrolled the Twentieth day of June, in the year of our Lord One
thousand eight hundred and thirty-four.