384 S. Webber on Ventilation. 
for the purest as well as the warmest air will be in the upper 
portion of the room, and if the lower air can be made to yield 
freelyto its downward pressure, as it accumulates by being pro- 
vided with a sufficient place of escape below, it will fill the whole 
room before, under ordinary circumstances, it can be rendered sen- 
sibly impure, and as fast as made so will be driven downwards 
and outwards by the continual fresh supply from the register. 
With a stove of any of the varieties of what in its simplest 
form is termed a box stove, in which fire burns freely by the ad- 
mission of a curreut of air.from the room, and. issuing through 
the funnel, there is a great economy of heat, but the ventilation 
is generally insifficient in a tight room, especially if a number of 
persons be present. Rooms so warmed ought to be provided 
with an additional ventilating aperture on a low level, and also 
with one on a high level for at least occasional use ; aud in order 
to make these properly effective, if the doors and windows be 
closely jointed or made impervious to the air in any considerable 
degree, a supply of fresh air should be bronght in, and conducted 
to the stove in some convenient way, so as to be sufficiently 
warmed before being diffused into the room. The Pollock stove 
mentioned in the beginning of this article, was a good adaptation 
of this principle. = + eerie! | 
What are called air-tight stoves, which have been greatly used 
within a few years past, while they economize fuel greatly, and 
