VENTILATION AND VENTILATORS. 
411 
The upper side of this cornice is composed of perforated zinc, 
which thus causes the air to be evenly distributed over the 
room. The holes are generally from to inch in diameter, 
and the area of the zinc perforated is to that of the air-spaces 
as about 6 to 1. 
Few systems are better adapted for the introduction of fresh 
air than that of the Barrack Commission above referred to, 
provided it is not required to heat the air before it is intro- 
duced. When the air has to be heated, a new set of contrivances 
is necessary. For ourselves, we think that, provided the cold 
air is brought into a well-heated room at such a level as to 
increase its temperature before it is breathed, and so distributed 
as to prevent draught, there is little necessity for any special 
device for warming it. In some cases, however, it appears to be 
necessary ; and various appliances have been employed in rais- 
ing it to its proper temperature. Of closed stoves for warming 
the air, there have been legion ; but, we think, in all cases they 
have proved objectionable, for they either burn the air which 
passes through them, and thus render it most unwholesome, or 
they impart to the heated air certain metallic impurities, which 
are not only offensive, but hurtful. There may be exceptions 
to this rule ; but, if so, we have not had the good fortune to 
meet with them. Of hot-water and steam apparatus, for the 
same purpose, we cannot speak in favourable terms ; they may, 
doubtless, be economical, but they are unsatisfactory from the 
two facts, that — 1. They produce an atmosphere which contains 
impurities arising from the heated tubes, and which is extremely 
distressing and unwholesome; and 2. That they are not un- 
attended with danger, from the circumstance that rupture of one 
of the pipes is likely to severely scald those in its proximity. 
The open fireplace seems in all cases to be the best means of 
warming, but it may be constructed so as to give out more heat 
than the average grate does, and may be contrived to supply 
warm air to a room. The following description of the open 
grate recommended by the Barrack Commissioners will demon- 
strate this. Though this grate is not absolutely new in prin- 
ciple, it is not constructed on any one of the old plans, but 
appears to be, as stated by Mr. Tomlinson, a combination of all 
the good points in the older inventions : tc The grate is placed 
as much forward in the room as possible. The part in which 
the fire is contained is of firebrick ; the bottom being partly 
solid, checks the consumption of fuel; a supply of air is 
admitted from behind the grate, and is thrown on the top of 
the fire to assist the prevention of the smoke. The sides are 
splayed so as to throw the heat, by radiation, as much as possible 
into the room. The opening into the chimney has no register. 
There is a chamber behind the grate into which air is brought 
