room, to supply what goes off through the opening of the chimney.
M. Gauger, a very ingenious and intelligent French writer on the
subject, proposes with judgment to admit it _above_ the opening
of the chimney; and to prevent inconvenience from its coldness,
he directs its being made to pass in its entrance through winding
cavities made behind the iron back and sides of the fire-place, and
under the iron hearth-plate; in which cavities it will be warmed, and
even heated, so as to contribute much, instead of cooling, to the
warming of the room. This invention is excellent in itself, and may
be used with advantage in building new houses; because the chimneys
may then be so disposed, as to admit conveniently the cold air to
enter such passages: but in houses built without such views, the
chimneys are often so situated, as not to afford that convenience,
without great and expensive alterations. Easy and cheap methods,
though not quite so perfect in themselves, are of more general
utility; and such are the following.
In all rooms where there is a fire, the body of air warmed and
rarefied before the chimney is continually changing place, and making
room for other air that is to be warmed in its turn. Part of it
enters and goes up the chimney, and the rest rises and takes place
near the ceiling. If the room be lofty, that warm air remains above
our heads as long as it continues warm, and we are little benefited
by it, because it does not descend till it is cooler. Few can imagine
the difference of climate between the upper and lower parts of such
a room, who have not tried it by the thermometer, or by going up a
ladder till their heads are near the ceiling. It is then among this
warm air that the wanted quantity of outward air is best admitted,
with which being mixed, its coldness is abated, and its inconvenience
diminished so as to become scarce observable. This may be easily
done, by drawing down about an inch the upper sash of a window; or,
if not moveable, by cutting such a crevice through its frame; in both
which cases, it will be well to place a thin shelf of the length,
to conceal the opening, and sloping upwards to direct the entering
air horizontally along and under the ceiling. In some houses the air
may be admitted by such a crevice made in the wainscot, cornish or
plastering, near the ceiling and over the opening of the chimney.
This, if practicable, is to be chosen, because the entering cold air
will there meet with the warmest rising air from before the fire, and
be soonest tempered by the mixture. The same kind of shelf should
also be placed here. Another way, and not a very difficult one, is
to take out an upper pane of glass in one of your sashes, set in a
tin frame, (Plate, Fig. 2.) giving it two springing angular sides,
and then replacing it, with hinges below on which it may be turned
to open more or less above. It will then have the appearance of an
internal sky light. By drawing this pane in, more or less, you may
admit what air you find necessary. Its position will naturally throw
that air up and along the ceiling. This is what is called in France
a _Was ist das?_ As this is a German question, the invention is
probably of that nation, and takes its name from the frequent asking
of that question when it first appeared. In England, some have of
late years cut a round hole about five inches diameter in a pane
of the sash and placed against it a circular plate of tin hung on
an axis, and cut into vanes, which, being separately bent a little
obliquely, are acted upon by the entering air, so as to force the
plate continually round like the vanes of a windmill. This admits the
outward air, and by the continual whirling of the vanes, does in some
degree disperse it. The noise only, is a little inconvenient.
2. A second cause of the smoking of chimneys is, _their openings
in the room being too large_; that is, too wide, too high, or
both. Architects in general have no other ideas of proportion
in the opening of a chimney, than what relate to symmetry and
beauty, respecting the dimensions of the room;[52] while its true
proportion, respecting its function and utility depends on quite
other principles; and they might as properly proportion the step
in a stair-case to the height of the story, instead of the natural
elevation of men's legs in mounting. The proportion then to be
regarded, is what relates to the height of the funnel. For as the
funnels in the different stories of a house are necessarily of
different heights or lengths, that from the lowest floor being
the highest or longest, and those of the other floors shorter and
shorter, till we come to those in the garrets, which are of course
the shortest; and the force of draft being, as already said, in
proportion to the height of funnel filled with rarefied air; and a
current of air from the room into the chimney, sufficient to fill
the opening, being necessary to oppose and prevent the smoke coming
out into the room; it follows, that the openings of the longest
funnels may be larger, and that those of the shorter funnels should
be smaller. For if there be a large opening to a chimney that does
not draw strongly, the funnel may happen to be furnished with the
air it demands by a partial current entering on one side of the
opening, and, leaving the other side free of any opposing current,
may permit the smoke to issue there into the room. Much too of the
force of draft in a funnel depends on the degree of rarefaction in
the air it contains, and that depends on the nearness to the fire of
its passage in entering the funnel. If it can enter far from the fire
on each side, or far above the fire in a wide or high opening, it
receives little heat in passing by the fire, and the contents of the
funnel is by that means less different in levity from the surrounding
atmosphere, and its force in drawing consequently weaker. Hence if
too large an opening be given to chimneys in upper rooms, those rooms
will be smoky: on the other hand, if too small openings be given to
chimneys in the lower rooms, the entering air, operating too directly
and violently on the fire, and afterwards strengthening the draft as
it ascends the funnel, will consume the fuel too rapidly.
_Remedy._ As different circumstances frequently mix themselves
in these matters, it is difficult to give precise dimensions for
the openings of all chimneys. Our fathers made them generally
much too large; we have lessened them; but they are often still
of greater dimension than they should be, the human eye not being
easily reconciled to sudden and great changes. If you suspect that
your chimney smokes from the too great dimension of its opening,
contract it by placing moveable boards so as to lower and narrow
it gradually, till you find the smoke no longer issues into the
room. The proportion so found will be that which is proper for that
chimney, and you may employ the bricklayer or mason to reduce it
accordingly. However, as, in building new houses, something must
be sometimes hazarded, I would make the openings in my lower rooms
about thirty inches square and eighteen deep, and those in the upper,
only eighteen inches square and not quite so deep; the intermediate
ones diminishing in proportion as the height of funnel diminished.
In the larger openings, billets of two feet long, or half the common
length of cordwood, may be burnt conveniently; and for the smaller,
such wood may be sawed into thirds. Where coals are the fuel, the
grates will be proportioned to the openings. The same depth is nearly
necessary to all, the funnels being all made of a size proper to
admit a chimney-sweeper. If in large and elegant rooms custom or
fancy should require the appearance of a larger chimney, it may be
formed of expensive marginal decorations, in marble, &c. In time
perhaps, that which is fittest in the nature of things may come to be
thought handsomest. But at present, when men and women in different
countries show themselves dissatisfied with the forms God has given
to their heads, waists and feet, and pretend to shape them more
perfectly, it is hardly to be expected that they will be content
always with the best form of a chimney. And there are some, I know,
so bigotted to the fancy of a large noble opening, that rather than
change it, they would submit to have damaged furniture, sore eyes,
and skins almost smoked to bacon.
3. Another cause of smoky chimneys is, _too short a funnel_. This
happens necessarily in some cases, as where a chimney is required in
a low building; for, if the funnel be raised high above the roof, in
order to strengthen its draft, it is then in danger of being blown
down, and crushing the roof in its fall.
_Remedies_. Contract the opening of the chimney, so as to oblige all
the entering air to pass through or very near the fire; whereby it
will be more heated and rarefied, the funnel itself be more warmed,
and its contents have more of what may be called the force of levity,
so as to rise strongly and maintain a good draft at the opening.
Or you may in some cases, to advantage, build additional stories over
the low building, which will support a high funnel.
If the low building be used as a kitchen, and a contraction of the
opening therefore inconvenient, a large one being necessary, at
least when there are great dinners, for the free management of so
many cooking utensils; in such case, I would advise the building of
two more funnels joining to the first, and having three moderate
openings, one to each funnel, instead of one large one. When there is
occasion to use but one, the other two may be kept shut by sliding
plates, hereafter to be described;[53] and two or all of them may be
used together when wanted. This will indeed be an expence, but not an
useless one, since your cooks will work with more comfort, see better
than in a smoky kitchen what they are about, your victuals will be
cleaner dressed, and not taste of smoke, as is often the case; and
to render the effect more certain, a stack of three funnels may be
safely built higher above the roof than a single funnel.
The case of too short a funnel is more general than would be
imagined, and often found where one would not expect it. For it is
not uncommon, in ill-contrived buildings, instead of having a funnel
for each room or fire-place, to bend and turn the funnel of an upper
room so as to make it enter the side of another funnel that comes
from below. By this means the upper room funnel is made short of
course, since its length can only be reckoned from the place where
it enters the lower room funnel; and that funnel is also shortened
by all the distance between the entrance of the second funnel and
the top of the stack: for all that part being readily supplied with
air through the second funnel, adds no strength to the draught,
especially as that air is cold when there is no fire in the second
chimney. The only easy remedy here is, to keep the opening shut of
that funnel in which there is no fire.
4. Another very common cause of the smoking of
chimneys, is, _their overpowering one another_. For instance, if
there be two chimneys in one large room, and you make fires in both
of them, the doors and windows close shut, you will find that the
greater and stronger fire shall overpower the weaker, and draw air
down its funnel to supply its own demand; which air descending in
the weaker funnel will drive down its smoke, and force it into the
room. If, instead of being in one room, the two chimneys are in
two different rooms, communicating by a door, the case is the same
whenever that door is open. In a very tight house, I have known a
kitchen chimney on the lowest floor, when it had a great fire in,
it, overpower any other chimney in the house, and draw air and smoke
into its room, as often as the door was opened communicating with the
stair-case.
_Remedy._ Take care that every room has the means of supplying itself
from without, with the air its chimney may require, so that no one of
them may be obliged to borrow from another, nor under the necessity
of lending. A variety of these means have been already described.
5. Another cause of smoking is, _when the tops of chimneys are
commanded by higher buildings, or by a hill_, so that the wind
blowing over such eminences falls like water over a dam, sometimes
almost perpendicularly on the tops of the chimneys that lie in its
way, and beats down the smoke contained in them.
_Remedy._ That commonly applied to this case, is a turncap made of
tin or plate iron, covering the chimney above and on three sides,
open on one side, turning on a spindle, and which, being guided or
governed by a vane, always presents its back to the current. This
I believe may be generally effectual, though not certain, as there
may be cases in which it will not succeed. Raising your funnels, if
practicable, so as their tops may be higher, or at least equal with
the commanding eminence, is more to be depended on. But the turning
cap, being easier and cheaper, should first be tried. If obliged to
build in such a situation, I would chuse to place my doors on the
side next the hill, and the backs of my chimneys on the furthest
side; for then the column of air falling over the eminence, and of
course pressing on that below and forcing it to enter the doors or
_Was ist das_es on that side, would tend to balance the pressure down
the chimneys, and leave the funnels more free in the exercise of
their functions.
6. There is another case of command, the reverse of that last
mentioned. It is where the commanding eminence is farther from the
wind than the chimney commanded. To explain this a figure may be
necessary. Suppose then a building whose side A happens to be exposed
to the wind, and forms a kind of dam against its progress. (Plate,
Figure 3.) The air obstructed by this dam will, like water, press and
search for passages through it; and finding the top of the chimney B,
below the top of the dam, it will force itself down that funnel, in
order to get through by some door or window open on the other side of
the building. And if there be a fire in such chimney, its smoke is of
course beat down, and fills the room.
_Remedy._ I know of but one, which is to raise such funnel higher
than the roof, supporting it, if necessary by iron bars. For a
turn-cap in this case has no effect, the dammed up air pressing down
through it in whatever position the wind may have placed its opening.
I know a city in which many houses are rendered smoky by this
operation. For their kitchens being built behind, and connected by a
passage with the houses, and the tops of the kitchen chimneys lower
than the top of the houses, the whole side of a street, when the wind
blows against its back, forms such a dam, as above described; and the
wind, so obstructed, forces down those kitchen chimneys (especially
when they have but weak fires in them) to pass through the passage
and house into the street. Kitchen chimneys, so formed and situated,
have another inconvenience. In summer, if you open your upper room
windows for air, a light breeze blowing over your kitchen chimney
towards the house, though not strong enough to force down its smoke
as aforesaid, is sufficient to waft it into your windows, and fill
the rooms with it; which, besides the disagreeableness, damages your
furniture.
7. Chimneys, otherwise drawing well, are sometimes made to smoke by
_the improper and inconvenient situation of a door_. When the door
and chimney are on the same side of the room as in the figure, if the
door A, being in the corner, is made to open against the wall (Plate,
Figure 4) which is common, as being there, when open, more out of the
way, it follows, that when the door is only opened in part, a current
of air rushing in passes along the wall into and across the opening
of the chimney B, and flirts some of the smoke out into the room.
This happens more certainly when the door is shutting, for then the
force of the current is augmented, and becomes very inconvenient to
those who, warming themselves by the fire, happen to sit in its way.
The _remedies_ are obvious and easy. Either put an intervening
skreen from the wall round great part of the fire-place; or, which is
perhaps preferable, shift the hinges of your door, so as it may open
the other way, and when open throw the air along the other wall.
8. A room, that has no fire in its chimney, is sometimes filled
with _smoke which is received at the top of its funnel and descends
into the room_. In a former paper[54] I have already explained the
descending currents of air in cold funnels; it may not be amiss
however to repeat here, that funnels without fires have an effect,
according to their degree of coldness or warmth, on the air that
happens to be contained in them. The surrounding atmosphere is
frequently changing its temperature; but stacks of funnels, covered
from winds and sun by the house that contains them, retain a more
equal temperature. If, after a warm season, the outward air suddenly
grows cold, the empty warm funnels begin to draw strongly upward;
that is, they rarefy the air contained in them, which of course
rises, cooler air enters below to supply its place, is rarefied in
its turn and rises; and this operation continues till the funnel
grows cooler, or the outward air warmer, or both, when the motion
ceases. On the other hand, if after a cold season, the outward air
suddenly grows warm and of course lighter, the air contained in
the cool funnels, being heavier, descends into the room; and the
warmer air which enters their tops being cooled in its turn, and
made heavier, continues to descend; and this operation goes on, till
the funnels are warmed by the passing of warm air through them, or
the air itself grows cooler. When the temperature of the air and of
the funnels is nearly equal, the difference of warmth in the air
between day and night is sufficient to produce these currents, the
air will begin to ascend the funnels as the cool of the evening comes
on, and this current will continue till perhaps nine or ten o'clock
the next morning, when it begins to hesitate; and as the heat of the
day approaches, it sets downwards, and continues so till towards
evening, when it again hesitates for some time, and then goes upwards
constantly during the night, as before mentioned. Now when smoke
issuing from the tops of neighbouring funnels passes over the tops of
funnels which are at the time drawing downwards, as they often are
in the middle part of the day, such smoke is of necessity drawn into
these funnels, and descends with the air into the chamber.
The _remedy_ is to have a sliding plate, hereafter described[55],
that will shut perfectly the offending funnel.
9. Chimneys which generally draw well, do nevertheless sometimes give
smoke into the rooms, _it being driven down by strong winds passing
over the tops of their funnels_, though not descending from any
commanding eminence. This case is most frequent where the funnel is
short, and the opening turned from the wind. It is the more grievous,
when it happens to be a cold wind that produces the effect, because
when you most want your fire, you are sometimes obliged to extinguish
it. To understand this, it may be considered that the rising light
air, to obtain a free issue from the funnel, must push out of its
way or oblige the air that is over it to rise. In a time of calm or
of little wind this is done visibly, for we see the smoke that is
brought up by that air rise in a column above the chimney. But when a
violent current of air, that is, a strong wind, passes over the top
of a chimney, its particles have received so much force, which keeps
them in a horizontal direction and follow each other so rapidly,
that the rising light air has not strength sufficient to oblige them
to quit that direction and move upwards to permit its issue. Add to
this, that some of the current passing over that side of the funnel
which it first meets with, viz. at A, (Plate IX. Figure 5.) having
been compressed by the resistance of the funnel, may expand itself
over the flue, and strike the interior opposite side at B, from
whence it may be reflected downwards and from side to side in the
direction of the pricked lines c c c.
_Remedies._ In some places, particularly in Venice, where they have
not stacks of chimneys but single flues, the custom is, to open or
widen the top of the flue rounding in the true form of a funnel;
(Plate, Figure 6) which some think may prevent the effect just
mentioned, for that the wind blowing over one of the edges into the
funnel may be slanted out again on the other side by its form. I have
had no experience of this; but I have lived in a windy country, where
the contrary is practised, the tops of the flues being _narrowed_
inwards, so as to form a slit for the issue of the smoke, long as
the breadth of the funnel, and only four inches wide. This seems to
have been contrived on a supposition, that the entry of the wind
would thereby be obstructed, and perhaps it might have been imagined,
that the whole force of the rising warm air being condensed, as it
were, in the narrow opening, would thereby be strengthened, so as
to overcome the resistance of the wind. This however did not always
succeed; for when the wind was at north-east and blew fresh, the
smoke was forced down by fits into the room I commonly sat in, so
as to oblige me to shift the fire into another. The position of the
slit of this funnel was indeed north-east and south-west. Perhaps if
it had lain across the wind, the effect might have been different.
But on this I can give no certainty. It seems a matter proper to
be referred to experiment. Possibly a turn-cap might have been
serviceable, but it was not tried.
Chimneys have not been long in use in England. I formerly saw a
book printed in the time of queen Elizabeth, which remarked the
then modern improvements of living, and mentioned among others the
convenience of chimneys. "Our forefathers," said the author, "had
no chimneys. There was in each dwelling house only one place for a
fire, and the smoke went out through a hole in the roof; but now
there is scarce a gentleman's house in England that has not at least
one chimney in it."--When there was but one chimney, its top might
then be opened as a funnel, and perhaps, borrowing the form from the
Venetians, it was then the flue of a chimney got that name. Such is
now the growth of luxury, that in both England and France we must
have a chimney for every room, and in some houses every possessor
of a chamber, and almost every servant, will have a fire; so that
the flues being necessarily built in stacks, the opening of each as
a funnel is impracticable. This change of manners soon consumed the
firewood of England, and will soon render fuel extremely scarce
and dear in France, if the use of coals be not introduced in the
latter kingdom as it has been in the former, where it at first met
with opposition; for there is extant in the records of one of queen
Elizabeth's parliaments, a motion made by a member, reciting, "That
many dyers, brewers, smiths, and other artificers of London, had
of late taken to the use of pit-coal for their fires, instead of
wood, which filled the air with noxious vapours and smoke, very
prejudicial to the health, particularly of persons coming out of
the country; and therefore moving that a law might pass to prohibit
the use of such fuel (at least during the session of parliament) by
those artificers."--It seems it was not then commonly used in private
houses. Its supposed unwholesomeness was an objection. Luckily the
inhabitants of London have got over that objection, and now think
it rather contributes to render their air salubrious, as they have
had no general pestilential disorder since the general use of coals,
when, before it, such were frequent. Paris still burns wood at an
enormous expence continually augmenting, the inhabitants having still
that prejudice to overcome. In Germany you are happy in the use of
stoves, which save fuel wonderfully: your people are very ingenious
in the management of fire; but they may still learn something in that
art from the Chinese[56], whose country being greatly populous and
fully cultivated, has little room left for the growth of wood, and
having not much other fuel that is good, have been forced upon many
inventions during a course of ages, for making a little fire go as
far as possible.