IMPROVEMENTS IN THE CONSTRUCTION AND ARRANGEMENT OF THE FLUES, AIR PASSAGES, AND OTHER PARTS OF FURNACES, AND ALSO IN CONTROLLING THE PASSAGE OF SMOKE AND IN HEATING AND REGULATING THE SUPPLY OF AIR TO FACILITATE COMBUSTION
Year: 1856

page_text: LETTERS PATENT to George Napier, of Bath Street, Glasgow, in the County
of Lanark, and of the Adelphi, in the County of Middlesex, Engineer, for
the Invention of "IMPROVEMENTS IN THE CONSTRUCTION AND ARRANGEMENT
OF THE FLUES, AIR PASSAGES, AND OTHER PARTS OF FURNACES, AND ALSO IN
CONTROLLING THE PASSAGE OF SMOKE AND IN HEATING AND REGULATING THE
SUPPLY OF AIR TO FACILITATE COMBUSTION."
PROVISIONAL SPECIFICATION left by the said George Napier at
the Office of the Commissioners of Patents, with his Petition, on the
26th January 1856.
P
I, GEORGE NAPIER, of Bath Street, Glasgow, in the County of Lanark, and
of the Adelphi, in the County of Middlesex, Engineer, do hereby declare the
nature of the said Invention for IMPROVEMENTS IN THE CONSTRUCTION AND
ARRANGEMENT OF THE FLUES, AIR PASSAGES, AND OTHER PARTS OF FURNACES, AND
ALSO IN CONTROLLING THE PASSAGE OF SMOKE AND IN HEATING AND REGULATING
THE SUPPLY OF AIR TO FACILITATE COMBUSTION, to be as follows:-
My Invention consists in the peculiar application and arrangement of two
or more furnaces, together with their several flues and passages, whereby the
smoke or gases of combustion of one fire are returned to the ash-pit of

page_text: another fire, through which the smoke and gases are passed, accompanied by
a certain admixture of air, while at the same time the fire from whence
the smoke and gases before mentioned is evolved is supplied with a proper
amount of heated air, which air is heated in a retort or heat chamber placed
in a smoke box or chamber between the boiler flues (when used for boilers)
and the chimney, and kept hot from the exterior by the waste heat passing
away from the boiler... The air so heated is conducted and admitted to the
ash-pit of the fire from which the smoke is being evolved, at the same time
air is otherwise excluded by an ash-pit door, which is kept closed at all times
except when open for the removal of ashes. By this means, when coaling or
otherwise stoking the fire, the volume of smoke which would escape unburnt
and pass off to the chimney is intercepted, and returned to an incandescent
fire, and so consumed.
For these purposes, I arrange valves in the several passages required to act
simultaneously and in connection with the furnace doors of the pair of furnaces
so placed in relation to each other, so that the act of opening one furnace door
closes the other, and at the same time establishes the several communications
by means of the valves to produce the change required, and vice versa;" the
doors can, however, be both closed at the same time, and are always so, except
when open for stoking purposes. Each furnace is furnished with a separate
air entrance passage, which conducts the air when required directly to the
passages of circulation in the heating chamber before mentioned, while at the
same time the smoke from fresh fuel circulates in similar and adjoining pas-
sages in the heat chamber, the air thereby becomes heated, and is conducted
thence to the ash pit of the fire, evolving smoke, while the smoke from that
fire returns to the bright fire. When change in the arrangement takes place,
these passages in the heat chamber are reversed; one which was before the air
passage becomes the smoke passage, while that which was the smoke passage
before is that through which the air now passes. The air inlet passages
when open to the heating chamber for the supply of the ash-pit of the fire
evolving smoke are fully open, but when closed to that channel are left
'partially open for the admission of a proportion of air to enter, which mixes
'with the smoke passing to the ash pit of the incandescent fire to assist its
combustion therein; any smoke and heat passing away from the bright fire,
after passing through the ordinary flues or tubes, passes on the exterior, and
envelopes the air-heating chamber before referred to, and thence to the
chimney, by which means the smoke & air in the heating chamber is dried
& heated.

page_text: A further improvement refers to the prevention of loss of heat by radiation
at the furnace door, which also assists in keeping the stoke hole cool. It con-
sists in forming a number of holes through the outer door of the furnace,
allowing a certain amount of cold air to enter between the outer and inner
doors; a slit or series of holes is or are also formed in the dead plate, so as to
permit the air thus entering between the outer and inner doors to pass freely
into the ash pit, the inner door being sufficiently close to prevent its direct
admission to the fire. A constant circulation of air is thus maintained between
the outer and inner fire doors, and the outer door thereby kept comparatively
cool.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said George Napier in the Great Seal Patent Office on the
26th July 1856.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, GEORGE:
NAPIER, of Bath Street, Glasgow, in the County of Lanark, and of the
Adelphi, in the County of Middlesex, Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-sixth day of January, in the year of our Lord
One thousand eight hundred and fifty-six, in the. nineteenth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said George Napier, Her special licence that I, the said George Napier, my
executors, administrators, and assigns, or such others as I, the said George
Napier, 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
THE CONSTRUCTION AND ARRANGEMENT OF THE FLUES, AIR PASSAGES, AND OTHER
PARTS OF FURNACES, AND ALSO IN CONTROLLING THE PASSAGE OF SMOKE AND IN
HEATING AND REGULATING THE SUPPLY OF AIR TO FACILITATE COMBUSTION," upon
the condition (amongst others) that I, the said George Napier, my executors
ór administrators, by an instrument in writing under or their, or one
of their hands and seals, should particularly describe and ascertain the
nature of the said Invention, and in what manner the same was to be
performed, and cause the same to be filed in the Great Seal Patent Office

page_text: within six calendar montis, next; and immediately after the date of the said
Letters Patent. '
NOW KNOW YE, that I, the said. George Napier; do hereby declare tho.
nature of, my said! Invention; and in what manner the same is to be per-.
formed; to be particularly, described and ascertained'in and by the following
statement; reference being had to the two Sheets of Drawings hereunto:
annexed, and to the letters and figures marked thereon (that is to say):
"
My Invention consists in the peculiar application and arrangement of two
or more furnaces,, together with their several flues and passages, whereby the
smoke or gases of combustion of one fire are returned to the ash pit of another
fire, through which the smoke and gases are passed, accompanied by a certain
admixture of air, while at the same time the fire from whence the smoke and
gas before mentioned is evolved, is supplied with a proper amount of heated
air, which air is heated in a retort or heating chamber, placed in a smoke box
or chamber situated between the boiler flues (when used for boilers) and the
chimney. This chamber is kept hot from the exterior by the waste' heat
passing away from the boiler. The air so heated is conducted and admitted
to the ash pit of the fire from which the smoke is. being evolved. Air is
otherwise excluded by ash-pit doors; which are kept closed at all times, except
when open for the removal of ashes. The smoke evolved in one fire, in
addition to being mixed with air, is at the same time passed through the
passages of the retort or heating chamber, whereby it is dried and heated
before it, is returned to the ash-pit of the other fire to be burnt. By this
means, when coaling or otherwise. stoking the fire, the. volume, of, smoke
which would escape unburnt and pass off, to the chimney. so intercepted, and
returned to an incandescent fire in a proper state for combustion.
11..
For these purposes, I arrange valves in the flues and air passages to act
simultaneously and in connection with the furnace doors of the pair of furnaces
so placed in relation to each other, so, that the act of opening.one,furnace door
closes the other, and at the same time establishes the several, communications
by means of the valves to produce the change required, and. "vice versa;" the
doors. can, however, be both. closed, at the same time, and, are always so,
except when open for stoking purposes. Eash furnace is, furnished with a
separate air entrance passage, which conducts the air when required
directly to the passage of circulation of the heating chamber before
mentioned, while at the same time the smoke from fresh fuel circulates
in. similar and adjoining passages in the heat chamber, the air thereby
becomes heated, and is conducted thence to the ash, pit of the fire, evolving

page_text: the smoke, while the smoke from that fire returns to the bright fire. When
change in the arrangement takes place, these passages in the heat chamber
are reverseil; one which was before the air passage becomes the smoke passage,
while that which was the smoke passage before is that through which the air
now passes. The air inlet passages when open to the heating chamber for
the supply of the ash-pit of the fire evolving the smoke may be fully open.
This air inlet, when closed to the fire producing the smoke, still remains
pártially open for the admission of a proportion of air to enter, which mixes
with the smoke, passing to the ash-pit of the incandescent fire to assist its
combustion therein; any smoke and heat passing away from the bright fire,
after passing through the ordinary flues or tubes, passes on the exterior, and
envelopes the air and smoke heating chamber or retort, before referred to, and
thence to the chimney, by which means the smoke and air in the heating
chamber is dried and heated.
A further improvement refers to the prevention of loss of heat by radiation*
at the furnace door, which also assists in keeping the stoke-hole cool. It
consists in forming a number of holes through the outer door of the furnace,*
allowing a certain amount of cold air to enter between the outer and inner
doors; a slit or series of holes is or are also formed in the dead plate, so as to'
permit the air thus entering between the outer and inner doors to pass freely
into the ash-pit, the inner door being sufficiently close to prevent its direct
admission to. the fire. A constant circulation of air is thus maintained
between the outer and -inner fire doors, and the outer door thereby kept
comparatively cool.
:
I would observe, that I am aware it has before been proposed to return the'
products of combustion of one fire to the ash-pit of another fire, and so pass
it through an incandescent' mass for combustion, and that what I regard' as'
novel & of my Invention in this respect is, the admixture of air with, such
products of combustion, and heating and drying the same in. the retort or
chamber, before mentioned, before it is returned to be consumed..
DESCRIPTION OF DRAWINGS.
Sheet one represents different views of the furnaces of a steam boiler fitted
and furnished for the purposes of and according to my Invention. In these
Figures I have 'represented two, furnaces, and so much of the boiler as necessary
for explanation; the same principle may, however, be carried out in an increased
number of fires. This boiler is adapted for land purposes, and may be built
in brickwork, or otherwise fitted, according to circumstances.

page_text: Fig. 1 is a front elevation of the lower part of a boiler; Fig. 2 is a hori
zontal section of the boiler, taken above the fires, on the line A, B, Fig. 4
which is a side view. Fig. 3 is a section on the line C, D, and through the
ash-pits and air flues, as herein used; while Figs. 5, 6, and 7, represent
different sections of the retort or heating chamber R, R, R. Section, Fig. 5
is taken on the line E, F, Figs. 2 and 4; section, Fig. 6, is taken at the line
I, J, Figs. 2 and 5; and section, Fig. 7, as taken on the line G, H, Figs. 2 and 5.
Supposing it is desired to throw coals on fire K, the door L of that fire is
raised by pulling down the handle a; there being a long slot 6 in the link con-
nection c, the door L may be so lifted without actuating any of the levers other
than d, with which it is connected. The action of the levers will be herein-
after described. When coals are thrown on this fire, the smoke and heat
evolved while playing on the bottom of the boiler will take the direction of the
block arrows, passing from furnace K to flue M, towards the front of the
boiler, up over the door by cross flue N, and descend to flue O, which is on
the same level as M. At the back part of flue O, a valve e is situated, which
in the present position of the gear is up, that is to say, open. In this position
it intercepts the passage of smoke in flue o towards the back, and causes it
to descend into passage P (which is also an air passage from front to back of
the boiler), following the dotted arrows, the smoke passes along the lower level
into the retort or heating chamber R, it passes up through interior flue Q and
down again to lower level, and thence returns to the ash-pit of fire T. During
this passage of the smoke it will be observed that the door to air flue P is
partially open (which must be regulated according to the requirements of com-
bustion, whereby a quantity of air is permitted to enter and mix with the smoke
in flue Q. The smoke and air in its progress through the passages Q, Q, Q,
becomes heated and dried, and rendered in a fit state for combustion, previous
to its passage through fire T. Any unconsumed gases and heat passing from
fire T follow the course of the black arrows, passing from fire T to flue V,
thence by cross flue V over the right-hand fire door to flue W, and proceeding
backwards meets with no obstruction from valve g (which is down and closed),
but passes directly into space J, H, and is caused to pass up, over, and to
envelope the retort R, R, by the outer casing X, X. Y is the passage to the
chimney. Thus, any heat passing from the fire T is caused to act on the retort
or heat chamber, and so operate on the air and gasses, as herein-before men-
tioned, whereby they are rendered fit for combustion before being returned to
the incandescent fire. The coals are to be thrown on fire K at the time
fire T is in an incandescent state, and the door. L being again closed, the

page_text: other parts remain as they were (by reason of slit b, as before mentioned),
when the combustion of the smoke will proceed. It will be observed that air
door f is partially open, and that air door t is full open, f admitting a small
quantity of air to be mixed with products of combustion from fire K before it.
passes through retort R on its passage to fire T, while t is full open and
admits air to ash-pit of fire K, but which air is previously dried and warmed.
by passing through flues 2, 2, in the retort and otherwise, as will be herein-after
more particularly described. The ash-pit doors are kept closed, except for the
removal of ashes, or other similar stoking purposes.
Previous to describing the change in the apparatus necessary for stoking firo
T, I will detail the several mechanical parts whereby the change is effected...
The doors Land Z are suspended from levers d and h, which move on fulcra i, k,
and are counterbalanced, so as to move readily, and also remain up or down,
(open or shut). l, m, are also two levers mounted on fulcra n, p. These levers.
1, m, are placed in connection with each other by a main lever q, mounted on a
fulcrum at r, so that any motion communicated to one of the levers l, m, is
transmitted to the other. Air doors, f, t, are suspended by links v, u, to the
levers l, m. The pins which connect the levers l, q, m, move in slit openings
in their ends, and also take into the slots b, b, in links c, c', which sloted links
move the system of levers, as will be herein-after described. The extreme ends
of the levers l, m, are connected with levers v, w, one on either side of the
boiler w, being distinctly seen in Fig. 4. These levers move on fulera x, x,
and are connected at the opposite end by links y, y, to arms z, z, fixed on the
axis on which the valves e and g move. When fire K has become incan-
descent, and fire T requires stoking, the following change takes place :-.
The pull handle a² of door Z is drawn down, whereby that door is raised
and opened; this at the same time throws the levers l, q, m, into the posi-
tion shown dotted, which has the effect of lifting the air down f, full open;
and at the same time nearly closing air door t. The valve e is brought down
and closes the passage between the upper flue O and lower flue P, and
valve g is at the same time raised, and establishes a communication between
flue W, and flue or air passages, immediately beneath. The position of these
valves are seen dotted in Fig. 4. Coals being thrown on fire T, the door Z
is pulled down and closed. The products of combustion now produced in
fire T will follow the course of the red arrows, passing by flue U into cross
flue V, over fire door Z, returning backwards by flue W; but the valve g
being up and open, the smoke is prevented passing at once into space H, I, of
retort, but descends through the opening of valve g into flue s, and thence into

page_text: it
up and down channels 2, 2, of the retort, from whence it returns by flue 3 to
the ash pit of the now incandescent fire K. The products of combustion mixed
with a due proportion of air are thus passed through the fire K. Any uncon-
sumed gas and heat from the fire proceed, as indicated by red arrows, through
the flues M, N, and O. The valve e being down and closed in this passage,
passes direct into space H, I, and envelopes the retort R before escaping
to the chimney at V, as before directed. The bottom of the boiler is imme-
diately above the fires K, T; and flues O, M, U, and W; and forms the
upper bounding surface of those flues. Instead of these flues being simply
divided by plates of metal, water spaces may be introduced between them,
and other separating parts may consist of water spaces, as well understood.
When fire T is incandescent, as first described, the door t is full open,
and air enters and passes along 's, s, and through passages 2, 2, in the retort,
wherein it is' dried and warmed; thence it proceeds by flue 3 to the ash-pit of
fire T, which has had fresh coals thrown on.
On the other hand, when fire T is in an incandescent state and fire K
charged with fresh coals, flue door f is full open, and permits free ingress of
air to channel P, which air passes into passages Q, Q, of the retort, and in its
passages becomes heated and dried, it then returns thence by flue S to the
ash-pit of fire K. It will be observed that when door f is full open to supply
the black fire, that door't is partially open for the admission and admixture
of a proportion of air with the products of combustion from that fire previous
to their passing to the bright fire; and vice versa. In addition to heat passing
outside the retort on its passage to the chimney, the air entering by the open
air is subject to the heat of the products of combustion passing simultaneously
by the flues or passages in the retort immediately adjoining, and it will be
observed that these flues are alternately the air flues' and smoke passages,
according as the change in the disposition of the parts takes place. .....
1. Sheet 2 represents different views and sections of a marine boiler repre-
senting improvements applied thereto. Fig. 1 is affront view; Fig. 2, is a back
view of á marine.boiler; two fires only are shown on these Figures, as being.
sufficient to illustrate the application of my improvements." Additional pairs
may, however, 'be added, taking care to combine each pair together with the
working gear and their several flues and passages, whereby the changes-herein-
after described may be accomplished. Fig. 3 is a horizontal section of the
boiler on the line 5,5; Figs. 3 and 4, and Fig. 4, is a horizontal section
taken on the line 6, 6, Eigs: 1 and 2; Fig. 5 is a section on the line L, L,
Figs. 1 and 3; Fig: 6, a section on the line 2, 2; Fig. 7, a section on the

page_text: line 3, 3; and Fig. 8, a section on the line 4, 4, Fig. 5. A and A' are the
fires, which are similar to the ordinary fires of marine boilers; B, B, the
bridges; the heat and flame from these fires does not pass directly over the
bridges towards and into the smoke boxes at the back, but after playing on
the fire surface of the boiler, comes in front and passes by the space C, imme-
diately over a closed chamber E at the fire door, into the smoke boxes D, D';
it then passes through the tubes F, G, into smoke boxes II and I, and from
thence by channels L, M, into the flues of the retort K, K, and is there
acted on and controlled in the manner described with: reference to the boiler
first herein-before set forth. The flues and passages of this retort or heating
chamber K, K, being differently arranged for this boiler, I will proceed to
describe its action. N, O, are the air inlet passages; N being the passage
having direct communicatión with fire A when that passage is full open, and
O the direct air passage to fire A when that, passage is full open; when these
passages are nearly closed the air entering proceeds to the opposite fires from
that just described.
The apparatus for regulating and effecting the changes in the flues and air
passages consists of a main lever P, mounted on a fulcrum at a; this lever
has a slot in either end, which receives the pins of two crank arms b, c; the
cranks b, c, are fixed on shafts e, f, which shafts pass through the boiler into
the retort, and are connected with the valves therein, the shaft e. having the
valve R, fixed on it, and also so furnished and fitted as to raise or depress the
valve S simultaneously therewith; valve T is fitted and fixed on.shaft f, while
the valve U is connected thereto by rod g and arm h, fixed to valve U, so that
any motion communicated to the valve T is transmitted. to valve U, so that
both move and change simultaneously. The furnace doors V and W are
suspended by levers i, k, on fulcra l, m, and are connected by slot links n, p,
so arranged, that the door. of the fire, having fresh coals on it, can be lowered
or raised at pleasure without disturbing the other door or levers; but when
the other fire is to be stoked, and its door opened for the purpose, the change
in the disposition of the valves and air passages is effected.
In the position
shewn in the Drawings, the fire A¹ is supposed to be that on which the fresh
coals are placed, and N the air passage by which air is admitted directly to
the ash-pit of that fire. The ash-pits are closed in front, except when open for
the 'removal of ashes, or other stoking purposes. The air is free to enter at N.by
reason of the valve S being raised; it passes through the retort passages X, X',
in the direction of the black arrow points, to the ash pit X" of fire A¹. The
products of combustion pass from this fire, pass by aperture C into smoke box

page_text: D', through the tubes G, G, G, to smoke box L, thence down channel M into
channel Y of the retort. The valve T being up, closes this passage from right
to left, Fig. 8. The valve U being. open the products of combustion proceed
through passage Z, Z, following the direction of the black arrows to the
ash-pit Z" of the incandescent fire A. During the progress of the smoke in
passage Z it is mixed with a certain quantity of air which is admitted at valvė
U, a stop being provided at that valve to prevent it entirely closing the air
admission passage; the air enters as indicated by the blue arrows.. During
the passage of the air and smoke through passages Y, Z and Z', they are mixed,
heated, and. dried before passing to fire A. In passing through bright fire A,
in thus prepared, the products are highly capable of combustion, and are con-
sumed therein; any unconsumed gases or products from fire A passing through
opening C into smoke box D, through tubes F, F, F, into smoke box H, thence
by down channel L into retort passage 7, and down into space 8, as indicated
by the black arrows; the valve S in its present position closes the passage 7
in the other direction. From space 8 the waste heat and products of com-
bustion escape by narrow channels 9, 9, passing up between the three flue
passages; after passing above the retort they are collected in the top plate 10, 10,
and escape thence to the chimney 15. The plate 11, 11, separates the top
cover 10, 10, from the upper part of retort flues, and the heat being distributed
over the entire area between those plates, it imparts heat through the plate.
11, 11, to the smoke flues. When fire A¹ becomes in an incandescent state,
and fire A requires coals thrown on, and the door is thrown up for that purpose,
the position of P is thereby altered, as indicated in dotted lines; the positions
of the valves R, S, T, U, are altered simultaneously by the rotary motion of
their shafts e and f, consequent on the opening of door J; the motion is im-
parted therefrom by lever i and link n to lever P, which acts on the the crank
arms b, c; of shafts e and f. The altered position of the valves R, S, T, and U
is represented in dotted lines in Figs. 3, 6, and 8. In the altered position
O becomes the free air ingress passage; the air passes along passage Z
following the direction of the red arrow points through Z into the ash-pit Zu
of fire A. The smoke and products of combustion evolved from this fire, after
heating the fire surface, passes by space C into smoke box D, through tubes
F, F, F, into smoke box H, thence, descending channel L into channel 7,
it follows the course of the red arrows through the passages X and X' into
ash-pit X of fire A. During the passage of the smoke through passage X, a
proportion of air is. admitted from air ingress apperture N, as indicated by
a yellow arrow, Fig. 6; the air thus entering is mixed with the product of

page_text: combustion in that passage. The smoke and air are heated and dried in
passage X before passing to fire A; to insure this, a stop 14 is provided, which
prevents valve S closing the air passage, which stop, can be regulated at.
pleasure according to the quantity of air required to be admitted. The course
of the remaining products of combustion, after passing through fire A', and the
heat from that fire, is up through space C³, smoke box D!, tubes G, G, G, and
into smoke box I, from thence it passes by down channel M into channel Y of
the retort. The valve T being open, as shewn dotted in Fig. 8, the waste
heat and unconsumed gases follow the course of the red arrow into space 8
below the upper retort flues, and thence escapes by channels 9, 9, to the
chimney 15, as before described with reference to the other fire. Instead of
the smoke passing at once from the fires to smoke boxes in front of the boiler,
as last herein-before described, it may first pass into the smoke boxes behind
through a lower series of tubes to the smoke boxes in front, and return-by
an upper series of tubes to upper smoke boxes at back, and from thence
proceed through the retort passages, to be there acted on as before described;
or it may first proceed from the fire through a series of short tubes to the back
of the boiler, thence through the retort passages, and back through an upper
series of tubes in the boiler to smoke boxes in front, and thence up to the
chimney.
Another part of my Invention relates to the admission of air to the space
between the outer and inner fire doors, and permitting it to pass from that
space down through holes in the dead plate or otherwise to the ash pit.
Fig. 5 represents, in section, the outer door K¹; and S, the inner door;
and E, the air space between. The door s is hinged at the lower part, and falls
down towards the outer door; it is so actuated when the door K' is opened
for the purpose of stoking, and raised again when that door is closed. This
motion is effected by lever t; mounted on a fixed fulcrum at u, and connected
at one end to the door K¹ by rod v, and at the other end by the rod w. to the
arm a, fixed on the axis of door s, thereby rendering the motion of the two
doors simultaneous. The air is admitted in constant streams through small
holes in the outer doors J and K, and becoming heated in space E, passes
thence through holes y, y, in the dead plates into the ash-pits. The quantity
of air admitted is regulated so that it is just sufficient to keep the outer door
cool and prevent much radiation of heat.
Having described the nature of my Invention, and the manner of performing
the same, I would have it understood that what I claim is,-
First, mixing the products of combustion of one furnace fire with air, and

page_text: heating and drying the products of combustion and air previous to return-
ing them to another. fire for combustion, combined with the arrangement and
combination of the fire doors of the furnaces, with valves in the air. and smoke
heating flues, as herein-before described.:
Secondly, I claim admitting air between the outer and inner fire: doors of
furnaces and passing it into the ash-pit, as herein-before described.
In witness whereof, I, the said George Napier, have hereunto set my
hand and seal, this Twenty-sixth day of July, in the year of our Lord
. One thousand eight hundred and fifty-six.
Witness,
W. CLARK, Patent Agent,
53, Chancery Lane, London.
GEO. NAPIER. (L.S.)