81 
APPLICATION OF HEAT. 
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General Subject. At a period when a great stimulus is given to the higher and 
more elegant departments of horticulture, by the reduction of duties which had long- 
lain as a dead weight upon its energies, it cannot he improper to take a retrospective 
view of the stages through which the processes of forcing and floriculture have passed 
from their rude commencements to their present state of comparative perfection. 
It were curious to retrace the appliances adopted and described by that Prince 
of Gardeners, Philip Miller, in his celebrated work the “ Gardener’s Dictionary,” 
published above a century ago, wherein we find the flues coursing backward and 
forward in the back walls of pine stoves, vineries, &c., &c. This mention of flues so 
situated leads to the consideration of that new scheme, now urged upon the public 
notice with a degree of pertinacity of which it appears very unworthy, under the title 
of the Polmaise System. 
It is utterly repugnant to our object to decry anything or any experiment which 
may conduce to improvement ; therefore, pending the arguments pro and con adduced 
by some who advocate or repudiate an arrangement which can in no degree affect 
the floral departments of the gardener, we now propose to take a passing glance 
of those methods of heating and applying bottom-heat which are manifest im_ 
provements upon the first inefficient flues in the back wall that have been above 
alluded to. 
The ordinary smoke flue, which has undergone every possible modification in its 
courses and positions, is on two accounts manifestly defective, the only exception (if 
so it can be considered) being the one figured in No. 143 of this Magazine, at page 
253. The first defect is inequality in the radiation of heat, by which the temperature 
of any house must vary in proportion. The second defect arises from altered condi- 
tions of the atmosphere, effected by the pervious nature of the brick channels through 
which the smoke and watery vapour, impregnated with sulphur and sulphurous acid, 
pass towards their final egress of the chimney. This defect cannot be perfectly 
remedied if even the steam of boiling water were thrown by a jet upon the burning 
fuel, so as to produce the entire combustion of the smoke ; because, though the 
formation of sooty black smoke might be prevented, the sulphurous ammoniacal 
gases would still pass along the flue and chimney, and penetrating the bricks, 
become intermixed with the atmosphere of the building. 
Here we call to mind the peculiar odour of a house heated by coals and coke, 
through the medium of smoke flues ; it is dry and unrefreshing : the sensation 
created on the skin appeals to the understanding, and seems to demonstrate that a 
healthy condition of foliage is wholly incompatible with a heated dry-stove. Hence 
the necessity of steaming, of pouring water upon flues, and of deluging the floor 
VOL. XIII.' NO. CXLVIII. M 
