156 
ON THE AERIAL SYSTEM OF FORCING. 
use, and constant repairs ? Boilers to unset, to clean, occasionally split, pipes oxi- 
dizing on the one surface, and choking up with incrustation on the other." 
All this is true, and much more. We have within five minutes' walk, a gentle- 
man's greenhouse, plant-house or grapery, according to the actual processes to which 
it may be, pro tempore, devoted ; it has a capital hot-water apparatus or triple range 
of cast-iron pipes, very conveniently fitted up ; the furnace also consuming any poor 
combustible matter, and little of it. Yet the prime cost of this machinery, we are 
told, exceeded £60, to say nothing of the house itself. And yet, this very complete 
arrangement of pipage might, and would be exposed to the same calamity which, not 
many years since, caused the loss of all the plants of a handsome conservatory. It 
happened that the year 1837 terminated with a temperature so mild, (nearly 50°) 
that the idea of fire never once occured ; the pipes were full, and all was safe ; but 
on the 3rd or 4th of January, 1838, the celebrated frost of that year set in at once. 
The whole volume of water froze, and, we believe, remained ice till destruction had 
done its work, for the fire from behind, (vis a tergo), could produce no effect upon 
a medium so non-conductive as that of ice. As the very reverse of this fatal visi- 
tation, a small vinery, furnished with an elaborate hot- water apparatus, suddenly lost 
an entire crop of fruit, by the intensely rapid heating of its tubes, which, defying 
regulation, raised the atmosphere to 100° in January. This was the result of a cost 
incurred a month or two before, and which exceeded £40 ! 
The defects, therefore, of our best machinery are manifest ; they do not equally 
heat the air of a house ; and so far as they do act by radiation, whether from hot 
brick flues, or from water tubes, or tiled channels, they render the atmosphere dry, 
and so far insalubrious. Now then, in order to remedy these defects, and to in- 
duce a constant interflow of fresh, warm air, charged with aqueous vapour, and 
therefore brought, as it were, into the condition of a new gas that can flow intersti- 
tially, and thus insinuate itself among the minutest particles of air already in the 
house, we must so arrange the apparatus that no particle of its hot surface be so 
exposed as to act by direct radiation. 
A considerable period must elapse ere we can hope to construct a furnace which 
will neither cause the loss of perhaps half its fuel by the chemical formation of car- 
bonic oxide, nor the diversion of the heat actually obtained, from its proper course ; 
but, notwithstanding, approaches have been made— and we had the satisfaction to 
inspect a stove which appeared to be built upon principles that gave promise, at least, 
of great prospective improvements in the construction of forcing-houses. This 
house had a span roof, with aspects to south and north ; also, corresponding front 
and back upright lights. The quarries are far too small, and the laps are not puttied ; 
therefore, from the extent of the glazed surfaces, it is peculiarly exposed to atmo- 
spheric influences. Yet by the situation of the furnace and its channels, all the heat, 
save that which escapes by the chimney-shaft, absolutely passes into the atmosphere 
of the house without any radiating surface whatsoever, and its equable diffusion 
appeared quite astonishing. 
