IMPROVEMENTS IN STEAM GENERATORS AND ENGINES
Year: 1874

page_text: LETTERS PATENT to Charles Lenton Abel, of No. 20, Southampton
Buildings, Chancery Lane, in the County of Middlesex, for the In-
vention of "IMPROVEMENTS IN STEAM GENERATORS AND ENGINES,"a
a-
communication from abroad by Edward A. L. Roberts, of Titusville,
PROVISIONAL SPECIFICATION left by the said Charles Denton Abel
at the Office of the Commissioners of Patents, with his Petition, on
the 18th July 1874.
I, CHARLES DENTON ABEL, of No. 20, Southampton Buildings,
Chancery Lane, in the County of Middlesex, do hereby declare the
nature of the said Invention for IMPROVEMENTS IN STEAM GENERATORS
AND ENGINES," to be as follows:-
This Invention relates to apparatus for the generation of steam and
for the treatment of the steam after it is generated, previous to its being
employed in the engine, and also to the construction of the cylinder and
Price Sd

page_text: piston of engines worked by steam, gas, or other elastic fluid; the
object being to provide a rapid exhaust for the steam, whereby back
pressure is almost entirely obviated and great rapidity of motion
attained.
·
The improved steam generator, which for the sake of clearness I will
describe as a vertical one, though it may also be employed in a hori-
zontal position, consists of a vertical cylindrical shell, which is divided
by a horizontal partition into a lower and an upper chamber, which for
convenience of reference I will term respectively the "prime boiler"
and the "auxiliary boiler." From the fire chamber at the bottom of
the generator a number of flue tubes pass upward through the prime
boiler and auxiliary boiler, terminating in the smoke box at the top of
the latter. Inside the prime boiler is a vertical cylinder of such a
diameter as to leave a space all round between it and the outer shell of
the boiler, which cylinder reaches to the water line or slightly above the
same, where it is open, and it rests with a flared edge on the bottom
plate of the boiler. In this flared edge, and also in the upper part of
the cylinder, are formed apertures, through which the water can
circulate, passing at bottom from the annular space outside the cylinder
to the inside of the same, and at top from the inside of the cylinder to
the external annular space. The water inside the cylinder being
necessarily hotter and consequently of a less specific gravity than that in
the external annular space, it will ascend inside the cylinder to the top
thereof, and will descend again in the annular space, whereby a perfect
and rapid circulation will be effected.
The cylinder instead of having a flared perforated bottom, as described,
may be cylindrical throughout and rest with short legs on the bottom of
the boiler, thus leaving a space at bottom through which the water
circulates.
The above described arrangement may be employed independently of
the auxiliary boiler, to be presently described, or in combination there-
with:
The auxiliary boiler is divided by horizontal diaphragms into two or
more compartments, through which the before-mentioned flue tubes
pass. The steam generated in the prime boiler is conducted through a
pipe into the top compartment of the auxiliary boiler, entering at one
side thereof. At the opposite side an opening is formed in the
diaphragm, through which the steam, after traversing the top compart-

page_text: :
ment (whereby it is brought into intimate contact with the hot flue
tubes) descends into the next compartment below, which it traverses in
like manner, and then descends through an opposite aperture in the
diaphragm into the next compartment, and so on, till the steam arrives
in the bottom compartment of the auxiliary boiler, whence it is conducted
through a pipe either directly to the engine or to another similar
apparatus if more than one is used.
The pipe through which the steam is led from the prime boiler to the
auxiliary boiler may be provided with a throttle valve controlled by a
governor actuated by the engine, so that according as the engine has
more or less work to do the supply of steam from the prime boiler to
the auxiliary boiler may be increased or diminished. Also the said
steam pipe may be combined with any suitable known form of injector,
whereby a certain quantity of air may be made to pass with the steam
into the auxiliary boiler; in which case a check valve is provided on the
injector to prevent the escape of steam from the auxiliary boiler when
the injector is out of action. Although I have described the auxiliary
boiler as being constructed in one with the prime boiler yet it will be
readily understood that it may be separate from the latter, provision
being made for the flue tubes to pass from the prime boiler through the
auxiliary boiler.
By the above described combination of the auxiliary boiler with the
prime boiler the saturated steam passing from the latter becomes
reheated and dried, and consequently increased in volume as it passes
through the auxiliary boiler in contact with the hot flue tubes; and by
the admission of air with the steam, as described, a larger amount of ·
the heat passing through the flue tubes is utilised in raising the tempera-
ture of the mingled air and steam.
In cases where two engines are worked together, so that they can be
driven by steam from the same boiler, the steam from the prime boiler
instead of being carried directly into the auxiliary boiler may be con-
ducted directly into one of the engines to work it; and the steam from
this engine may be made to exhaust into the auxiliary boiler, where it
is reheated and conducted thence into the second engine. Or the steam
may be conducted from the prime boiler into the steam jacket of the
engine cylinder, and thence into the auxiliary boiler, whence after being
reheated it is conducted into the engine cylinder to work the engine.

page_text: According to the second part of this Invention the cylinder of an
engine is provided at the middle of its length with a circumferential
aperture or port extending all round it communicating with a passage
formed round the outside of the cylinder, which is in connection with
the exhaust. At each end of the cylinder are the ordinary steam and
exhaust ports provided with slide or other valves of usual construction
for admitting and exhausting the steam to and from the cylinder. The
piston of the cylinder is constructed of a length equal to one half the
length of the cylinder or equal to the length of the stroke, less the width
of the before-mentioned central circumferential port, so that at the end of
the stroke of the piston the said port may be entirely uncovered by the
piston, and shall be closed by the passage of the piston over it at the
commencement of the stroke and remain so closed until the termination
of the stroke.
The operation of this improved construction of the cylinder and piston
is as follows: On the admission of steam on the top of the piston to
give the down stroke the piston descends immediately, covering the
before-mentioned central exhaust port in the cylinder. When the
piston arrives near the end of its down stroke it begins to uncover the
central exhaust port, through which the steam on top of the piston will
then escape, so that by the time the piston has completed its down
stroke and has completely uncovered the central port the steam will have
been almost entirely exhausted through the large area of the port; and
the remaining steam, if any, having no greater or very slightly greater
pressure than that of the atmosphere will readily exhaust through the
ordinary exhaust port when the piston at the commencement of its
up stroke has again closed the central exhaust port. By thus furnishing
a double exhaust by the above-described construction the back pressure
experienced in engines of ordinary construction is obviated, which back
pressure, particularly in engines running at a high speed, causes a great
loss of power.
Another advantage of the central exhaust port is that
when the cylinder is in a horizontal position any water of condensation
therein will readily flow off through such central port at each stroke,
instead of accumulating in the cylinder, as in engines of ordinary
construction.
The circular passage, into which the steam exhaust from the central
port, may have an opening by which the steam may be allowed to escape
into the atmosphere while the ordinary axhoust unuta

page_text: a pipe with a condenser, so that the engine may be used either as non-
condensing or as a condensing engine, as may be desired.
The improved construction may also be advantageously applied to
compound engines by connecting the exhaust from the central exhaust
port to the second cylinder, and the exhaust from the slide valve with
the condenser; thus using the first cylinder both for high and low
pressure.
In the use of a low-pressure engine the cylinder can be perfectly
exhausted by means of the central exhaust port, and the ordinary exhaust
ports to the slide valves may be dispensed with.
. Instead of constructing the central exhaust port as a continuous
aperture extending all round the cylinder it may extend only partially
round the cylinder, or it may consist of a series of apertures extending
all round.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Charles Denton Abel in the Great Seal Patent
Office on the 16th January 1875.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, CHARLES
DENTON ABEL, of No. 20, Southampton Buildings, Chancery Lane, in
the County of Middlesex, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Eighteenth day of July, in the year of
our Lord One thousand eight hundred and seventy-four, in the thirty-
eight year of Her reign, did, for Herself, Her leirs and successors,
give and grant unto me, the said Charles Denton Abel, Her special
license that I, the said Charles Denton Abel, my exccutors, adminis-
trators, and assigns, or such others as I, the said Charles Denton Abel,
my executors, administrators, and assigns, should at any time agree with,
and no others, from time to time and at all times thereafter during the
term therein expressed, should and lawfully might make, use, exercise,
and vend, within the United Kingdom of Great Britain and Ireland,
the Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS
IN STEAM GENERATORS AND ENGINES," a communication to me from abroad by
Edward A. L. Roberts, of Titusville, County of Crawford, Pennsylvania,

page_text: United States of America, upon the condition (amongst others) that
I, the said Charles Denton Abel, my executors or administrators, by an
instrument in writing under my, or their, or one of their hands and seals,
should particularly describe and ascertain the nature of the said Inven-
tion, and in what manner the same was to be performed, and cause the
same to be filed in the Great Seal Patent Office within six calendar
months next and immediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Charles Denton Abel, do hereby
declare the nature of the said Invention, and in what manner the same
is to be performed, to be particularly described and ascertained in and
by the following statement thereof, reference being had to the accom-
panying Sheet of Drawings, and to the figures and letters marked
thereon, that is to say :--
This Invention relates to apparatus for the generation of steam and
for the treatment of steam after it is generated previous to its being
employed in the engine; and also to the construction of the cylinder
and piston head of steam, gas, air, or other like engines, the object being
to provide a rapid exhaust for the steam, whereby back pressure is
almost entirely obviated and great rapidity of motion attained, together
with several other incidental advantages, which will hereafter be more i
particularly referred to.
I will first proceed to describe the improved steam generator, referring
to Fig. 1 of the accompanying Drawings for that purpose, which shews
a perspective view of the steam generator partly in section, as also a
perspective view of the improved steam cylinder, which will be hereafter
described.
The improved steam generator or boiler is here shown as a vertical
cne, and as such will be described in the following Specification, although
it will be obvious the improvements may be applied to horizontal boilers
by modifications of arrangement readily understood.
In the Drawing a is a vertical cylinder forming the outer case or shell
of a boiler, underneath which at b is the furnace, from the fire-chamber
of which vertical flues e of any desired number and size pass upwards
through the steam generator c, and also through the upper chamber d,
communicating with the smoke stack or flue f at their upper end. For
convenience of reference I term the steam generator c the "prime
.
:

page_text: boiler," and the upper chamber d the "auxiliary boiler." Where they
are constructed together, as in the Drawing, the prime boiler c and
auxiliary boiler d are separated by a horizontal diaphragm g, through
which the flues c, e, pass, but without any communication through it
between the prime and auxiliary boilers. Inside of the prime boiler is a
cylindrical shell, with a flared bottom i. This cylindrical shell h
rests on the bottom of the boiler, surrounding and enclosing the vertical
flues e, e, e, and extending upwards to or a little above the water line.
The flared bottom i is perforated with holes for the passage of the
water from the outside of the plate, and the upper part of the cylindrical
shell may also be perforated with a series of smaller holes for the
passage of the water from the inside of the shell . The object of this
cylindrical shell is to secure and maintain a rapid circulation of water
within the boiler. It is well known that in boiling water the hot water
together with the bubbles of steam rises toward the surface, while the
colder water descends to the bottom of the boiler, thus causing a cir-
culation. But where, as is usual, there is no device for giving direction
to this circulation, there are a number of currents ascending and
descending, which impinge against each other and interfere with the
process. By the use of this perforated shell the water at the bottom
of the boiler heated by the fire passes up through the interior of the
shell, causing an ascending column. This heated water passes out
through the perforations 1, 1, or over the top of the shell if it is sub-
merged, and descends around the outside of the shell / to the bottom of
the boiler, where it enters the perforations in the flared bottom i of
the shell, and again ascends as before described. Thus a well defined
circulation is maintained throughout the water in the boiler, the effect
being a more rapid generation of steam. By thus separating the
ascending and descending currents of water the circulation becomes
more rapid, and the heat is more effectually extracted from the flues by
the water. The effect of the use of the shell is so marked in practice
that the ascending water, being the lighter column, will be perceptibly
higher in the centre of the boiler over the shell h than at the circum-
ference outside of it, and by this means the water comes in contact with
a more extended surface of the heated flues.
The apparatus so far described forming the prime boiler may be used
independently of the auxiliary boiler, which I am about to describe, or
in connection with it, as may be preferred. If used in connection with

page_text: the auxiliary boiler a pipe m connects the upper part of the prime boiler
with the upper part of the auxiliary boiler d, so that the steam generated
in the prime boiler is introduced directly into the auxiliary boiler. On
this pipe m the throttle or governor valve may be placed, for reasons
which will be hereafter explained.
The auxiliary boiler d, through which the flues e, e, pass, as before
described, is furnished with horizontal diaphragms n, n, the number of
which may be varied at pleasure according to the size of the apparatus.
These diaphragms are connected closely with the interior surface of the
sides of the boiler for about nine-tenths of its circumference, a space
being left between each diaphragm and the interior surface of the boiler
for about one-tenth of the circumference. If preferred, the diaphragms
may extend so as to connect all around with the interior surface of the
side of the boiler, and may be perforated at one point, as shown at a, so
as to produce the same effect as the construction before described. These
spaces or perforations in the diaphragms are alternately on opposite
sides of the boiler. The uppermost diaphragm having the space located
an the opposite side of the boiler to that at which the steam enters
through the pipe m, the effect of this arrangement is that the steam
entering through the pipe m above the uppermost diaphragm passes.
horizontally between it and the top plate of the auxiliary boiler across
the boiler to the perforated portion of the diaphragm or open space, and
having no other exit passes through the space downwards and hori-
zontally across the boiler in the opposite direction between the uppermost
or first diaphragm to the space or perforation in the second diaphragm,
and so on across the boiler and through the spaces between the dia-
phragms in the direction of the arrows in the Figure until it reaches the
bottom of the auxiliary boiler, where between the lowest diaphragm
and the bottom of the auxiliary boiler is the exit pipe o, from which
steam passes to the engine or to another similar apparatus, if more than
one is used.
I have described the steam as entering the auxiliary boiler from the
prime boiler through the pipe m, designing to be understood that the
connection between the pipe m and the auxiliary boiler is a close one,
but I have shown in the Drawing an injector inserted in the auxiliary
boiler at the point where the steam is introduced from the pipe m.
this case the connection between the pipe m and the auxiliary boiler is
not close, but is through the injector, which is so constructed in any
In

page_text: known way as to cause the steam in entering the auxiliary boiler from
the pipe m to carry with it a current of atmospheric air from the out-
side. At the end of the injector pipe inside of the auxiliary boiler is a
check valve p designed to prevent the return of steam and air. It is
preferred so to construct the apparatus which I have described as to
place the auxiliary boiler immediately on top of the prime boiler
separated only by a diaphragm g, as shown in the Drawing, for the
more convenient passage of the flues e, e, through the auxiliary boiler,
and also in order to utilize the heat of the prime boiler; but as I have
already intimated the auxiliary boiler may be made separate, and con-
nected with the prime boiler in such a way as to allow of the passage
of the flues through the former if preferred.
The operation of the apparatus thus described is as follows:-Steam
generated in the prime boiler at a high pressure is saturated with
aqueous vapour. The steam is passed into the auxiliary boiler, which is
of such size as to allow the steam to expand to double the volume, more
or less, which it occupied in the prime boiler. In this auxiliary boiler,
in which no water is introduced other than that which may come in
through the steam pipe m, the steam is reheated by the waste gases of
the furnace passing through the flues e, e, and any aqueous vapour or
water introduced with the steam is converted into steam. By this means
the volume of the steam is largely increased, while its efficiency is not
correspondingly reduced, and thereby a great saving of power is effected.
When air is introduced with the steam through the injector the air
becomes heated and acquires great expansive force, and has the effect of
keeping the steam dry. The mingled steam and heated air pass out
through the pipe o to the engine, where it is used in the same manner
as steam as a motive power.
In steam boilers of ordinary construction where the throttle valve or
governor valve is placed on the pipe connecting the steam generator and
the engine it often happens that the steam in the boiler is of much
When this
greater pressure than is necessary to be used in the engine.
occurs there is a manifest waste of heat, but by placing the throttle or
governor valve on the pipe m between the prime boiler and the auxiliary
boiler the admission of steam into the auxiliary boiler is regulated by
the requirements of the engine, and when the admission of steam into
the auxiliary boiler is lessened by means of the valve the fires under the
prime boiler may be let down to such an extent as may be indicated by

page_text: the pressure gauge, while the steam in the auxiliary boiler being of
reduced temperature will have correspondingly greater power to absorb
heat from the waste gases which pass through the flues c.
Another advantage of the admission of air with the steam in the
auxiliary boiler is that the air coming from the outside and mingling
with the steam reduces its temperature, and utilises a larger amount of
the waste heat of the gases passing from the pipes e in raising the
temperature of the mingled air and steam. In addition to this the
expansive force of the steam is expended in forcing the air in the boiler,
which greatly increases the volume of gases to propel the engine.
In cases where two engines are worked together, so that they can be
driven by steam from the same boiler, the steam from the prime boiler,
instead of being carried directly into the auxiliary boiler, may be con-
ducted directly to one of the engines to work it, and the steam from this
engine may be made to exhaust into the upper end of the auxiliary boiler,
in which case an air injector is not required, and it is there reheated
and thence conducted to the second engine to operate it.
Another mode in which this apparatus may be used is to conduct
steam directly from the prime boiler to a properly jacketted cylinder of
the engine, and the steam after passing around the cylinder may then be
conducted directly to the auxiliary boiler, from whence after being re-
heated it
passes to the engine to operate it. By this means the tempera-
ture of the cylinder is not only kept uniform, but is preserved at about
the temperature of the steam from the auxiliary boiler, which is used
to operate it, for if this cylinder should be too cool it would be heated
by the steam from the prime boiler, or if on the other hand the reheated
steam from the auxiliary boiler should be hotter than that in the prime
boiler the steam from the prime boiler would prevent the cylinder from
becoming unduly heated, the excess of heat being communicated to the
steam passing around outside of the cylinder before it enters the auxiliary
boiler.
The shell instead of having a flaring perforated bottom, as has been
described, may be made cylindrical throughout, and be furnished with
short legs resting on the bottom of the boiler, and thus leaving a space
between the bottom of the plate and the bottom of boiler for the
entrance of the current of water from the outside to the inside of the
shell h

page_text: I will now proceed to describe my improvements in steam engines,
referring to Figs. 1 to 4 of the accompanying Drawings, of which Fig. 1
shews a perspective elevation of a steam cylinder with the said improve-
ments applied thereto; Fig. 2 shews a longitudinal section to an enlarged
scale through the axis of the cylinder; Fig. 3 shews a
through the cylinder, one-half to the right-hand side being on line X, X,
Fig. 2, and the other half on line Y, Y, Fig. 2; Fig. 4 shews the width and
circumferential length of the central steam escape port of the cylinder!
cross section
A, A, represents the cylinder of an engine, which may be made of
any ordinary construction, excepting in the particulars herein-after
specified. About midway from either end of the cylinder is a slot or
aperture B, which extends circumferentially around and communicates
with the interior of the cylinder. This aperture should be of such width
as to provide a rapid exit for the exhaust steam. At each end of the
cylinder are the ordinary ports C and D for inlet and exit of steam,
which are connected in the usual or any suitable manner with a slide or
other valve E for operating the engine. The circumferential slot B is
covered over by an annular belt F, which may be cast in one piece with
the cylinder, and which arches over the circumferential slot so as to
form a steam way G all around the cylinder, thus forming an annular
exhaust port, which has a large opening or pipe H at any convenient
point on the cylinder, which should be of sufficient diameter to afford a
free exit for the exhaust steam. In addition to the exhaust provided by
the central slot already described the cylinder is also furnished with the
ordinary exhaust ports I in the slide valve E. The object of this
double exhaust will be explained more fully hereafter. The cylinder A'
is furnished with a piston head K, the length of which in the line of its
axis should be one-half the length of the cylinder or the length of the
stroke, less the width of the central slot B, so that at the end of either
the up or down stroke of the engine the central part B may be entirely
uncovered by the piston head K, and shall be closed at the commence-
ment of either stroke, and remain so closed by the piston head until the
termination of the stroke.
The operation and construction of the piston head is as follows:-On
the admission of steam on top of the piston to give the down stroke the
piston descends, immediately covering the central port B, which remains
closed until the upper edge of the piston head reaches the upper edge of
the slot B, and at the completion of the down stroke of the engine the

page_text: slot B is entirely uncovered. This immediately relieves the pressure of
steam in the upper part of the cylinder, the steam escaping all around
and passing through the annular steam way or port G and out through
the pipe H. As soon as the piston head K has reached this point the
return or up stroke commences, the annular slot B being immediately
covered, as before described, and the remaining steam in the upper part
of the cylinder having no greater or very slightly greater pressure than
that of the atmosphere, escapes through the upper port or exhaust in
the slide valve.
The object of this construction of cylinder and piston, furnishing a
double exhaust, obviates the difficulty experienced in the construction
of engines, both locomotive and stationary, of the back pressure of the
steam on the piston head, which proves a very serious loss of power,
especially in engines running at a very high rate of speed, and which
frequently amounts to a loss of at least twenty-five per cent. The
ordinary method of partially overcoming this difficulty is to open the
exhaust port at about two-thirds stroke so as to leave the cylinder
sufficiently exhausted to relieve the back pressure on the return stroke.
This is manifestly done at a great sacrifice of power on the last third of
the stroke.
By means of the construction I have described the full elastic force
of the steam can be used during nineteen-twentieths of the stroke.
From what has been said it is evident that as the piston head uncovers
the central slot at the end of each stroke when it is on its dead centre
the piston is at that moment theoretically at rest, allowing an appre-
ciable time for the steam to escape through the slot B and steam way G
around it. Attached to the slide valve, and connecting with its exhaust
port I, a pipe L may be introduced connecting with the condenser, so
that the engine may be used both as a low and high pressure engine,
as may be desired. In case of a low-pressure engine the steam is thus
instantly exhausted into the condenser, but in the case of a high-pressure
engine the steam which is left in the cylinder to balance the external
atmospheric pressure is exhausted through the ordinary slide valve
exhaust port.
The before described improvement may also be very advantageously
applied in the use of a compound engine by connecting the exhaust
from the central slot to the second cylinder, and the exhaust from the

page_text: slide valve with the condenser, thus using the first cylinder both for low
and high pressure.
There are several very important incidental advantages connected
with the use of this improvement which I will briefly refer to. It is
obvious that the cylinder constructed as I have described may be placed
either vertically or horizontally, and if used as a horizontal engine the
difficulty ordinarily arising from the presence of the water of condensa-
tion in the cylinder is entirely obviated, as such water will pass off
through annular slot B into the exhaust pipe H connected therewith,
and will be discharged at every stroke with the exhaust steam.... In case
of the use of the improved cylinder and piston as a low-pressure engine
the cylinder can be perfectly emptied or exhausted at each stroke by
means of the central slot B into the condenser, and the cylinder will
require only two or more openings or valves to admit the steam at either
end, as before described. Hence a great advantage in cutting off steam,
which can be perfectly regulated by means of the governor without any
contraction of the exhaust.
Another advantage is that as the spent steam is continually exhausted
at the middle of the cylinder around the piston head it serves as an
admirable lubricant to the piston. Also as the piston passes over the
circular slot or port all pressure of steam is relieved between the surface
of the cylinder and the piston head, thus preventing any unequal side
pressure or wear between the surface and that of the piston head or its
rings, allowing the rings to be expanded so as accurately to fit the
cylinder, thus making the tendency of the piston head to wear round
and true.
The increased length of the piston head, and consequent increased
length of the cylinder, give increased wearing or bearing surface, which
not only gives greater parallelism of motion and less vibration but also
considerably lessens the liability of leakage of steam.
The practical effect of the present improvements is that the engine
can be run at a vastly increased rate of speed, owing chiefly to the
absence of back pressure, rapidity of exhaust, and also in some measure
to the other advantages before referred to. This greatly increased.
rapidity of motion prevents in a great degree the change of temperature
of the surface of the cylinder which occurs in taking and exhausting
steam in engines of comparatively slow motion, thus retarding the con-

page_text: densation of the steam in the cylinder and the chilling of the live steam
as it enters.
i
Engines constructed with the present improvements may be run at a
speed of from one to three thousand revolutions a minute, thus securing
a high degree of power in a small engine. Such engines may therefore
be connected directly, without the introduction of gearing, or pulleys and
belts with fast running machinery, such as circular saws, propellers, &c.
I have described the cylinder in this Specification and accompanying
Drawings as being furnished with an ordinary D slide valve, but valves
of any other desired construction may be employed. I have also
described the central exhaust as being a slot extending all round the
cylinder. This however may be varied by the use of a series of apertures
extending around or partially around the cylinder. Or if a slot is used
it may also extend partially around instead of completely surrounding
the cylinder as described.
"Having thus described the nature of this Invention, and in what
manner the same is to be performed, as communicated to me by my
foreign correspondent, what I claim is,-
First. The use in steam generators of the auxiliary boiler d furnished
with diaphragms, and traversed by flues from the furnace, and connected
with the prime boiler by suitable pipe or pipes, substantially as and for
the purposes herein-before described.
Second. The use in steam generators such as are above referred to of
the cylindrical shell placed on the bottom of the boiler and surround-
ing the flues for the purpose of giving direction to the currents of water
and producing a definite circulation in the boiler, substantially as herein-
before described.
::
:
Third. The use in combination: with steam generators, such as are
above referred to, of an injector interposed between the prime and
auxiliary boiler, for the purpose of introducing air with steam into the
latter, substantially as and for purpose herein-before specified.
Fourth. The method, substantially as herein described, of superheat-
ing the mixture of air and steam by passing the same through the
auxiliary boiler of steam generators such as are above referred to.
Fifth. The method of passing steam from the prime boiler of steam
generators, such as are above referred to, into the jacket of the steam
cylinder of an engine, and thence into the auxiliary boiler.

page_text: Sixth. The use in steam cylinders of an exhaust port extending around
or partially around the middle of the cylinder in combination with an
annular exhaust passage, substantially as herein described.
Seventh. The use in combination with the middle exhaust port above
referred to of a piston of such length as to open the said port at or near
the end of each stroke, and close it during the rest of the stroke, sub-
stantially as herein-before described.
In witness whereof, I, the said Charles Denton Abel, have hereunto
set my hand and seal, this Fifteenth day of January, in the
year of our Lord One thousand eight hundred and seventy-
five.
CHA³. D. ABEL. (L.S.)