3* 
HEAT AND ITS APPLICATION. 
To resume the subject of heat as applied to forcing-houses, it must be again 
impressed, that any combustible body, be the material what it may, can only cause 
the diffusion of heat in a volume of air, to an extent proportionate to the chemical 
energy exerted between the elements of water and carbon, when they combine by 
mutual attraction ; but that the heat so induced may, nevertheless, be squandered 
or economised by the machinery applied. 
There is perhaps nothing more wonderful in nature than the extrication of 
light and heat. We daily, hourly, throughout our lives, become witnesses of 
phenomena perfectly miraculous ; and pass them by as mere matters of course ; — 
yet in the ignition of a common lucifer-match there is a power revealed equally 
mysterious as that which causes a flash of lightning to dart from the East to 
the "West. 
But we must not, in a notice purely practical, attempt to enter upon an 
inquiry concerning causes : it is well, however, when a mind accustomed to scan 
the mysteries of nature with stolid indifference, becomes aroused in a degree to 
some appreciation of their beauty and truth. 
In our last, an attempt was made to describe a simple machinery by which a 
portion of coke, kept at a state of moderate red-heat in a cylindrical vessel, was 
enabled to communicate its heating power to a body of water, so as to effect all 
the objects of forcing hitherto attempted by the means of fermenting beds of dung, 
leaves, tan ; and by fire-flues, whether employed separately, or in conjunction ; but 
till within the few past weeks we were not aware of the great extent to which the 
principle might be applied ; — and now, in order to direct the amateur or professed 
gardener, who contemplates an erection, either as a propagation-house, flower-stove, 
or pinery, wherein any degree of heat from 55° to 75° can be at absolute command, 
we will describe a water-flue or channel, which is actually at work, and can at 
any time be efficiently regulated. 
The objections to the coke furnace, before urged, remain in their full force ; 
but as to the water-channels now alluded to, they appear to be almost perfect. For 
example : — suppose a hot-house twenty-five feet long from east to west, and nine 
or ten feet wide from back to front ; the boiler, capable to contain five gallons, 
may be erected at any convenient part outside of the back wall, so that its flow 
and return pipes shall pass through that wall, where they may communicate with 
the water-flues or channels ; at this place they are on a perfect level, the fall being- 
provided for by the rapid descent of the return-pipe. A platform of earth is then 
raised all round the house, secured by brick facing- walls ; and herein some care 
is required to obtain a correct and solid foundation, at about two feet above the 
ground level. 
Upon this platform courses of two bricks are laid flat, end to end, and securely 
vol. xi r. — no. cxxxiv. F 
