MODIFICATION OF POLMAISE HEATING. 
81 
The house was built originally for a cool or late vinery ; but when it became 
the object of the proprietor to excite one department, and to leave the larger 
division as a cool house, he determined to see how far it might be possible to keep 
up a constant interchange of air, without lowering the temperature of the house, by 
the ingress of a current of cold air from without. 
To effect this purpose, the pit No. 1 was covered with loose boards, so correctly 
fitted as to confine the air within, heated by the flue, and to permit none to escape, 
excepting by a square opening (marked □) about six inches in diameter, and raised 
an inch or two above the surface of the boarding by four strips of wood ; this 
covering, and indeed every part of the woodwork, is painted pure white, rather 
flatted, which, with the predominance of fine glass, produces an effect of lightness 
that is very uncommon. At the mark ai is made a trough or channel of wood, 
that can be closed by a sloping flap with hinges, when not in use. It stands level 
at top with the eastern side-light, and passes below the surface of the ground, where 
it is connected with a series of six-inch earthen pipes, which enter the pit No. 1, 
but pass no further than the inner surface of the pit's wall ; and thus the air of the 
external atmosphere may be made to enter the pit, or be taken off at pleasure. 
Finally, at the circular mark 0 at w, is an orifice made at the level of the ground, 
close to the south-east corner, between the east door and the front wall; it passes 
through the wall, and is connected with a course of six-inch earthen tubes which 
are led with a gradual downward slope under the ground outside, but very near the 
foundation of the wall, and enter the ash-pit of the furnace; thus completing 
the aerial circle. 
Having witnessed the lighting of the first fire, and been a party in the operation, 
the perfect action of the draught by the flue and chimney was ascertained without a 
doubt. When a certain time had elapsed sufficient to bring the flue of the first 
division to a degree of sensible heat, the ash-pit door was completely closed and the 
flap ai raised to admit air by that channel into the pit. The fire, therefore, could 
no longer be excited by any external current ; it must and did receive its entire 
supply of air through the channel of the earthen tube which had its origin at 0, 
close to the south-east corner. Yet the fire drew perfectly, the smoke passed through 
the chimney-pot with decision, insomuch that, when the masonry became heated, 
it was necessary to check the draught by pushing in the chimney-damper. Another 
proof of successful operation was required, and that consisted in holding a slender 
shaving of wood over the opening, (marked □). It moved up and down, thus 
proving the existence of a gentle stream of air passing to and from the pit upwards, 
and vice versa ; and as the ascending air communicated sensations of warmth to the 
face when presented at some distance above the orifice, the chain of proofs became 
completed ; and thus, if we comprehend the proposed object by the advocates of "Pol- 
maise" a current of warm air, refreshed and renewed by the admission of the external 
atmosphere, has been obtained, and constantly kept up, by the simple machinery of 
afire-flue. 
VOL. XIV. NO. CLX. M 
