CHIMNEYS. 13 
by fliding plates, hereafter to be defcribed*; and two or all 
of them may be ufed together when wanted. This will 
indeed be an expence, but not an ufelefs one, fince your 
cooks will work with more comfort,. fee better than in a 
fmoky kitchen what they are about, your victuals will be 
cleaner drefled and not tafte of {moke, as is often the cafe; 
and to render the effect more certain, a ftack of three fun= 
nels may be fafely built higher above the roof than a fin- 
gle funnel. 
The cafe of too fhort a funnel is more general than 
would be imagined, and often found where one would not 
expedt it. For it is not uncommon, in ill-contrived build- 
ings, inftead of having a funnel for each room or fireplace, 
to bend and turn the funnel of an upper room fo as to 
make it enter the fide of another funnel that comes from 
below. By this means the upper room funnel is made 
fhort of courfe, fince its length can only be reckoned from 
the place where it enters the lower room funnel; and that 
funnel is alfo thortened by all the diftance between the en-= 
trance of the fecond; funnel and the top of the ftack: For 
all that part being readily fupplied with air through the 
fecond funnel, adds no ftrength to the draft, efpecially as. 
that air is cold when there is no fire in the fecond chim- 
ney. The only eafy remedy here is, to. keep the open- 
ing fhut of that funnel in which there is no fire. 
4. Another very common caufe of the {moking of 
chimneys, is, their overpowering one another. For in- 
ftance, if there be two chimneys in one large room, and you 
make fires in both of them, the doors and windows.clofe 
fhut, you will find that the greater and ftronger fire fhall 
overpower the weaker, and draw air down its. funnel to 
fupply its own demand; which air defcending in the 
weaker funnel will drive down its fmoke, and force it into 
the room. If, inftead of being in one room, the two chim- 
neys are in: two different rooms, communicating by a door, 
the cafe is the fame whenever that door is open. In a very 
tizht 
* Sce Appendix, N.O HH. 
