414 
POPULAR SCIENCE REVIEW. 
in the grate. This is quite sufficient to produce a very power- 
ful out-draught of air, while it adds nothing to the temperature 
of the room ; its expense, too, is slight compared with the 
benefit it confers, and there is little difficulty in arranging it, as 
a flexible varnished tube may easily be carried to the burner 
from a joint fixed in the neighbouring gas-pipe. 
Had we not already transgressed the limits originally assigned 
to our remarks, we should have entered on the subject of 
mechanical systems of ventilation — such arrangements as the 
steam-fan employed in the Eeform Club House, the furnace of 
the House of Commons, the air-ffiters of the Post Office, the 
steam-jet employed by Dr. Edmonds in ventilating the lower 
decks of ships, the heated-tube system of Mr. Sutton for a 
similar purpose, and various other contrivances, whose names 
alone constitute a formidable list ; but we must draw our obser- 
vations to a close. What we have said, has been said rather with 
a view to draw the attention of the thoughtful to a subject of 
the most vital interest, than to convey the idea that any per- 
fectly satisfactory scheme of ventilation has yet been proposed. 
Our aim has been to lay before our readers a general expression 
of the conditions as to the quality of air necessary for healthy 
ventilation. This, we think, has not hitherto entered suffi- 
ciently into the considerations of those who have pursued the 
study of methods instead of principles. It must, nevertheless, 
be admitted that no system of ventilation can be satisfactory 
unless it be in accordance with the laws of hygiene. Of these 
laws, as they relate to ventilation, we have given our readers 
a general idea ; and we would, in conclusion, assure them that 
since they are capable of mathematical demonstration, they must 
inevitably form the basis of every efficient plan for the main- 
tenance of a healthy atmosphere in our private dwellings and 
public buildings.* 
* With one or two exceptions, the woodcuts illustrating- this article have 
been borrowed from Weales’ excellent treatise on “ Warming and Ventila- 
tion.” For the stereotypes we are indebted to the courtesy of Messrs. Virtue. 
