gf VmtUatmg and Warming Buildings. ^69 
t)rdinary circumstances, common flange pipes, of from three to 
:five inches interior diameter, and cast as thin as they can be cast, 
sound and perfect. Double cylinders, one of which is shown by 
Fig. 5. Plate II., and its section in Fig. 4, may, in other cases, 
be used with advantage, as they afford a large quantity of si*r- 
face ; and by introducing a pipe A, for fresh air, into the cen- 
tral part of the cylinder, it warms the air as it enters the room. 
The top and the base fit on to the cylinder, and it is supplied 
with steam from the wrought iron-pipe B, and the air and con- 
densed water are taken away by the pipe C. The admission of 
fresh air is to be regulated by the handle D. The steam occu- 
pies the space between the two cylinders at «, «, in the section. 
It is necessary that the cylinder should have an open top, as 
shown at E ; and as the height should not exceed about three 
feet, it is requisite to make the open work ornamental. 
In other instances, I have used pipes joined in short lengtl 
IS, 
nearly in the form of a distiiler'’s worm, and placed an open 
itrellis screen over them. 
The proportion of pipe required to heat a given quantity 
of air per minute is easily calculated, by the following formula: 
.48 C (T — t) 
jeOO — T 
i — superficial content of surface of steam-vessel 
-that will lieat C cubic feet of air, from the temperature t 
to T, in one minute. Therefore, the quantity of ventilation 
-and loss of heat per minute, being ascertained by the prin- 
ciples already given for ventilation, it is easy to provide the 
requisite supply of heat. It is assumed, that the pipes are 
of cast-iron, that being the fittest material, except for the small 
conveying pipe, which may be of wrought-iron ; but other sur- 
faces will afford about the same quantity of heat, if of a dark 
colour, and the surface a little rough and spongy: a bronze 
colour is very well adapted for giving of heat. 
In applying steam-heat, it should always be made to warm 
that part of the air which is introduced for ventilation, before it 
enters the rooms ; but it shoidd only be warmed to a tempera- 
ture a little lower than the mean temperature of the room ; the 
proportion of pipe to be applied for that purpose our formula will 
show, and a register to regulate the quantity which enters, will 
put it in the power of ^ny person to alter it at pleasure. 
