154 
ON THE AERIAL SYSTEM OF FORCING. 
In our last article upon the equable diffusion of heat in plant-houses > 
attempt was made to show that almost every species of machinery in use, and eai 
attempt to modify or improve the same, had been erected and regulated up L 
erroneous principles. We have two important, paramount objects in view — econor 
of money and fuel, and the utmost attainable equability of temperature within tl 
area of the building. There is no desire to interfere with the views of the opulen 
we perceive the very extensive desire that exists among persons of limited proper 
to cultivate and protect the plants which they admire ; and therefore, if it 
possible, we would enable the amateur to possess himself of the best appliances 
the least possible outlay. 
Fuel of any description can hut afford a certain quantity of heat ; and if we ev 
admit, that, by any possibility, the whole inflammable matter of a combustible 
absolutely consumed, so as to give forth its heat, it still may happen that a maj 
part of the heating power will never enter into the atmosphere of a house. A vet 
few months have elapsed since it was proved by one of our philosophical lecture 
that when coke, charcoal, and particularly pit coal, is burned in stoves of commi 
form, the coal itself that lies above the portion that is in a state of actual combustion is 
part dissolved, and carried into the chimney in the state of carbonic oxide , an inflai 
mable gas which, under other circumstances, would take fire, give out its heat, ai 
be itself converted to carbonic acid ; a gas which is the result of complete combustio 
and in itself capable of extinguishing fire or flame with the utmost rapidity. Tl 
cylindrical, double-cased, hot-water boilers not long since so much in vogue, yie 
demonstrative proof of the distillation of unconsumed fuel ; for at the very time wh< 
the coke immediately above the bars is, to the height of four or five inches, in 
state of active red heat, the cooler fuel above, recently supplied, shall appear qui 
and inactive till atmospheric air from above is admitted, by removing the cast-in 
air-tight cover which secures the summit of the inner cylinder, when an explosr 
puff of pale-blue tinted flame will rush through the cylinder, to a height that migf 
seriously injure the incautious operator when examining the state of the fuel. Tb 
circumstance alone, connected as it is with the loss of so much inflammable matte 
ought to disqualify these dangerous boilers. 
Since the announcement of the Polmaise system, with its paraphernalia of hi 
plates and wet blankets, the writer has had occasion to inspect some erections, ar 
to bestow observation upon multitudinous articles on the merits and defects of tl 
so-called system. The result is, that attempts to prove too much on the one sid 
and virulent abuse, replete with disgraceful falsity on the other, have thrown du: 
into the eyes of the sincere inquirer after truth, and equally retarded the progre; 
onward toward the right path. But all this while the original Polmaise has passe 
