Prof. Hosking on Ventilation. 255 
grate by a metal or pot pipe, up the chimney flue, and be deliv- 
ered in any upper room next to the same flue and requiring 
warmth and ventilation, the process of ventilation applied to the 
lower room being applicable to the upper room also. 
The indicated means by which winter ventilation is obtained 
are not of course equally efficient in summer, for the draught of 
the fire is wanting ; but the inlet at the lower level for fresh air, 
and the outlet for the spent air at the upper level continuing 
always open, the heat which the fiue will in most cases retain 
through the summer aided by that of the sun’s rays upon the 
chimney top, secures a certain amount of up-draught, which is 
not without its effect upon the in-draught by the lower ‘inlet 
even when windows and doors are shut. . 
While it is obvious that ‘the air drawn into any house for the 
purpose of in-door ventilation need not be other than that which 
would enter by the windows of the same house, it may be ne- 
cessary to enter into an inquiry as to the condition of the air 
heretofore spoken of as fresh and pure. Fresh” and “ pure” 
applied to air must be taken to mean the freshest and purest im- 
mediately obtainable, and that will be ‘the same whether it be 
drawn in through a grated hole in a wall, or by a glazed open- 
ing closed by it in the same wall. But it is a fair subject for in- 
quiry, whether,—speaking in London to Londoners,—the air 
about our houses in London is as pure,—or as free from impurity 
—as it might be. 
€ out-door ventilation of large towns may be taken to be 
more complete above the tops of the houses and of their chim- 
heys than it is, or, perhaps, can be among and about the houses. 
The processes of nature are there not only unchecked, but are 
in fact aided by the heat thrown up by the chimneys into the 
Upper air, and impurities which can be passed off by chimney: 
flues, will be more certainly and more effectually removed and 
changed by nature’s chemistry than if they are kept down to 
fester under foot and to exhale in our streets and about our doors 
and windows. 
At this time every endeavor is made to provide for removing 
from our dwellings all excrementitious matter, and all soluble 
teluse, by drains into sewers, and so by the sewers to some out- 
fall for discharge. The drain necessarily falls towards the sewer, 
and the sewer again to its outfall, and the sullage or soil drainage 
being rendered liquid thus passes in the usual course. Dut t 
usages and the necessities of civilized “life cause a large propor- 
ion of the liquid refuse from dwelling-houses to pass off in 
eated state, or to be followed by hot water arising from culinary 
Processes, and from washing in all its varieties. ‘The heat so en- 
tering the drains causes the evolution of fetid and noxious gases 
