Notices respecting New Books. 283 
swer very well to produce heat, which may be marked by the 
thermometer; but more than this is wanted in a conservatory 
for invalids or delicate subjects. 
<< A supply of warm air must be had; but not merely warm 
air; it must possess all its vital principles. There must be a 
circulation of air through the apartments, that is, the air which 
has served the purposes of respiration and combustion must have 
a free egress, and fresh-charged atmospheric air be freely ad- 
mitted ; for it is proved by the experiments of Messrs. Lavoisier, 
Guyton, Fourcroy, and Davy, that the common atmospheric air, 
from the Frozen Ocean to the equator, consists of the same 
component parts; the only difference between the air of En- 
gland and of the most favoured climate depends upon its pro- 
portion of caloric. The best means I know of answering this 
purpose, is by placing a stove in the lowest part of the house, 
which stove is to heat porcelain tubes, through which the at- 
mospheric air will be conveyed into a large main pipe going 
from the bottom to the top of the building; from this pipe cur- 
rents of warm air may be directed into any apartment, in the 
same manner as water is conveyed from a reservoir placed at 
the top of the house, in pipes, to all the various parts below its 
level, following the laws of specific. gravity. As heated air has 
specific levity with regard to the atmospheric air, if we have a 
reservoir of heated air in the lowest part of the house, we may 
convey it from the bottom to the top, by the same laws as we do 
the water fromabove. Thisis the mode of heating the Madeira 
House, by thus throwing into any given apartment a current of 
warm air. If there be a small fire in the room, the air which 
that consumes will be brought into the reom by the warm air 
pipe: whereas, in a room not supplied with this current of warm 
air, the firé will draw the air it requires either through crevices 
in the windows or through the door, causing cold currents of 
air, playing upon the persons in the room between these crevices 
and the fire. In this new mode of ‘giving warm air to a room, 
instead of the room drawing cold air from without, it becomes 
filled with warm air, and is ready to expand itself through all 
erevices. Thus double windows, which are recommended by 
Count Rumford, and almost universally adopted in the north of 
Europe, are rendered unnecessary. There is, in this case, a 
universal plenum ; in the other, to avoid the vacuum, the air 
rushes in from all parts. In a room which I have appropriated 
for my study, I have not had a fire for the two last years. I 
have a pneumatic stove, which throws in warm air; it issues 
from the aperture at 100 degrees up to 150, and diffuses itself 
so as to keep the room at the temperature of 60. 
* In the common mode of warming rooms, the great difficulty 
is, 
