¢ 
* 
S. Webber on Ventilation. 875 
Here seem to be all the contrivances that Professor Hosking 
has bronght forward, save the ventilating aperture into the chim- 
ney above, and she. moveable valve in the throat of the flue 
which alone can render that aperture necessary for ordinary pur- 
‘poses. Even this moveable valve in the smo ue has been in 
use from time immemorial in Russian stoves and for a vast many 
years under the name of a@ damper, in the close stoves in our 
own country. It is an objectionable piece of apparatus without 
the accompaniment of a ventilator, since poe ap at in any. 
eserrabte degree the escape of t t froma room or from 
e fire, it likewise prevents the Nickie oe the carbonté acid gas 
pate by respiration and combustion. But even with a close 
Stove, if this be not used, or used only in a slight degree, so as 
to permit a free draught of air throngh the stove, unless the 
room be over-crowded with persons, there will be s — ven- 
tilation for the ordinary purposes of health and scabies “he 
opening by which the air has access to the fire in the stove isa 
sufficient ventilator 
Mr. Hosking,’ however, thinks it sagidntant that the opening 
should be near the ceiling of the room. If it be so placed it 
will counteract, in some degree, what he is endeavoring to ob- 
tain by his contrivances below, that is, warmth and purity of air, 
by co nveying away almost perhaps as fast as it enters, the warm 
fresh air brought in by his heated air pipes s below, as the hotest 
air will most readily escape from-an opening in the top of = 
room, and that/just delivered from the heated supply pipes 
openings, will probably be the hottest. But his re a aa 
Statements on the condition and action of the air are so loose an 
unscientific, that it may be well, in order to present the ee 
ully, to go into.a little examination of them 
e says, “ open a window in an otherwise close room and no 
air will enter; no air can enter indeed, unless force be applied as 
with a bellows, whereby as much may be driven out as is driven 
in, with the-effect only of diluting not of purifying.”, 
‘Now so far from this being generally true, it can be so only 
under particular and somewhat rare circumstances, acta when 
the air in the close room shall be of precisely the same tempera- 
ture, and the same specific gravity as the ésattrenl air. Ifthe 
air contained i in the room be warmer than the external air, imme- 
diately upon opening the window a double current will be estab- 
lished through the opening, an inward current of cold : at the 
bottom of the opening, and an outward current of warm 
top... This double current will continue to act with full olde till 
the cold air has replaced the warmer air of the room up tot 
bottom of the open: window, The force of action will then be 
diminished and the depth d till 
the cold air has risen-to the top of the ———” 
