1851.) OF THE ROYAL INSTITUTION. ik 
breath, asit leaves the nostrils heated by the fire in the lungs, rises, or 
seeks to rise, above their level, and may not be again inhaled. Out of 
doors the cooler or less heated air of the lower level presents itself 
for respiration unaffected by the spent exhaled air, but in a close 
apartment the whole body of included air must soon be affected by 
whatever process any portion of it may have undergone. The process 
by which Nature carries off spent air, purifies, and returns it 
uncontaminated, is thus checked by the circumstances under which 
we place ourselves within-doors. All our devices for shelter from 
the weather, and for domestic convenience and comfort, tend to 
prevent the process provided by Nature from taking effect according 
to the intention in that respect of the Creator. We not only confine 
ourselves, indeed, and pen up air in low and close rooms, but, we 
introduce fire by which to warm the enclosed air; wanting light 
within our dwellings when daylight, fails, we introduce another 
sharer in the pent-up air of our rooms, being fire indeed in another 
form, but generally under such circumstances, that it not only ab- 
stracts from the quantity, but injures the quality of what may remain, 
But fire, whether in the animal system, in the grate, or in the lamp, 
cannot long endure the imagined limitation of air. ‘There must be 
access of air — of vital air-—-by some channel or other, or the fire 
will go out. 
An open fire in the grate must however have a vent for some 
of its results, or it will be so disagreeable a companion that its 
presence could not be endured, even as long as the most limited 
quantity of air would last; and the fire will compel the descent of air 
by the vent commonly supplied under the name of a flue—a chimney 
flue — to render its presence tolerable in a closed room, if a supply 
be not otherwise obtainable. But as the outer air at the higher level 
of the top of a chimney, because of the rarity of the air in and above 
the flue, responds to the demand of the fire less easily than the 
lower air, or that at and about the level of the fire; and the lower 
air, or air at the lower levels, forces its way in, therefore, by any 
opening it can find or make — through the joints of the flooring- 
boards and under the skirtings — the supply passing first up or 
down the hollow lathed and plastered partitions, sometimes even 
up from the drains; and through the joints under and about the 
doors and windows. If these channels do not exist, as they may not 
when the joiners’ work and the plastering are good, or when the open 
joints referred to are stopped up by any means, the fire smokes, and 
every known means of curing the chimney failing, means are sought 
of obtaining heat without the offending fire. Ventilation is not 
thought of yet. 
The open fire may be made to give place to the close stove or to hot 
air-pipes, to hot-water pipes, or to steam pipes—which make hot the air 
about them in a close room without causing draughts. But the 
warmth obtained in pipes is costly under any circumstances. Air 
does not take up heat freely, unless it be driven and made to pass 
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