8 LE.T T E R° concErninec 
the opening of the chimmey into the funnel which prevents 
the fmeke coming out into the room, if you fupply. the 
funnel by other means or in other ways with the air it 
wants, and efpecially if that air be cold, you diminifh the 
force of that current, and the {moke in its efforts to. enter 
the room finds lefs refiftance. 
The wanted air muft then zndi/penfably be admitted into 
the room, to fupply what goes off through the opening 
of the chimney. M. Gauger, a very ingenious and in- 
telligent French writer on the fubje&, propofes with 
judgment to admit it above the opening of the chimney ; 
and to prevent inconvenience from its coldnefs, he directs 
its being made to pafs in its entrance through winding 
cavities made behind the iron back and fides of the fire- 
place, and under the iron hearth-plate; in which cavities 
it will be warmed, and even heated, fo as to contribute 
much, inftead of cooling, to the warming of the room. 
This invention is excellent in itfelf, and may be ufed with 
advantage in building new houfes ; becaufe the chimneys 
may then be {fo difpofed, as to admit conveniently the cold 
air to enter fuch paflages: But in houfes built without 
fuch views, the chimneys are often fo fituated, as not to 
afford that convenience, without great and expenfive al- 
terations. Eafy and cheap methods, though not quite fo 
perfe& in themfelves, are of more general utility; and 
fuch are the following. 
In all rooms where there is a fire, the body of air warm- 
ed and rarefied before the chimney is continually changing 
place, and making room for other air that is to be warm- 
ed in its turn. Part of it enters and goes up the chimney, 
and the reft rifes 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, becaufe it does not defcend till it is cooler. Few can 
imagine the difference of climate between the upper and 
lower parts of fuch a room, who have not tried it by the 
thermometer, 
