6 LETTER concernine 
and expe& impoffibilities. Yet under this fituation, I 
have feen the owner of a new houfe, in defpair, and ready 
to fell it for much lefs than it cofl, conceiving it unin- 
habitable, becaufe not a chimney in any one of its rooms 
would carry off the fmoke, unlefs a door or window were 
left open. Much expence has alfo been made, to alter 
and amend new chimneys which had really no fault; in 
one houfe particularly that 1 knew, of a nobleman in 
Weftminfter, that expence amounted to no lefs than three 
hundred pounds, after his hovfe had been, as he thought, 
finifhed and all charges paid. And after all, feveral of the 
alterations were ineffectual, for want of underftanding the 
true principles. 
Remedies. When you find on trial, that opening the 
door or a window, enables the chimney to carry up all 
the {moke, you may be fure that want of air from with- 
out, was the caufe of its fmoking. I fay from without, 
to guard you againft a common miftake of thofe who may 
tell you, the room is large, contains abundance of air, 
fufficient to fupply any chimney, and therefore it cannot 
be that the chimney wants air. Thefe reafoners are igno- 
rant, that the largenefs of a room, if tight, is in this cafe 
of {mall importance, fince it cannot part with a chimney 
full of its air without occafioning fo much vacuum ; which 
it requires a great force to effe&, and could not be borne 
if effected, 
It appearing plainly, then, that fome of the outward 
air muft be admitted, the queftion will be, how much is 
abfolutely neceffary ; for you would avoid admitting more, 
as being contrary to one of your intentions in having a 
fire, viz. that of warming your room. To difcover this 
quantity, fhut the door gradually while a middling fire is 
burning, till you find that, before it is quite fhut, the {moke 
begins to come out into the room, then open it a little till 
you perceive the {moke comes out nolonger. There hold 
the door, and obferve the width of the open crevice be- 
tween 
