CHIMNEYS. 9 
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 beft admitted, with 
which being mixed, its coldnefs is abated, and its incon- 
venience diminifhed fo as to become fearce obfervable. 
This maybe eafily done, by drawing down about an inch 
the upper fafh of a window; or, if not moveable, by cut- 
ting fuch a crevice through its frame ; in both which cafes, 
it will be well to place a thin fhelf of the length, to con- 
ceal the opening, and floping upwards to diredt the enter- 
ing air horizontally along and under the ceiling. In fome 
houfes the air may be admitted by fuch a crevice made in 
the wainfcot, cornifh or plaftering, near the ceiling and 
over the opening of the chimney. ‘This, if practicable, 
is to be chofen, becaufe the entering cold air will there 
meet with the warmeft rifing air from before the fire, and 
be fooneft tempered by the mixture. The fame kind of 
fhelf fhould alfo be placed here. Another way, and not 
a very difficult one, is to’ take out an upper pane of glafs 
in one of your fafhes, fet it in a tin frame, giving 
it two fpringing angular fides, and then replacing fit! 
it, with hinges below on which it may be turned ~ 
to open more or lefs above. It will then have the ap- 
pearance of an internal fky light. By drawing this pane 
in, more or lefs, you may admit what air you find necef- 
fary. Its pofition will naturally throw that air up and 
along the ceiling. ‘This is what is called in France a Was 
fi das? As this is a German queftion, the invention is 
probably of that nation, and takes its name from the fre- 
quent afking of that queftion when it firft appeared. In 
England, fome have of late years cut a round hole about 
five inches diameter in a pane of the fath and placed againft 
ita circular plate of tin hung on an axis, and cut into 
vanes, which being feparately bent a little obliquely, are 
acted upon by the entering air, fo as to force the plate con~ 
tinually round like the vanes of a*windmill. This ad- 
B mits 
