C8 THE FLORIST’S JOURNAL. 
alluded to : and nothing but the erroneous impression, “ that 
there is an affinity between the particles of air and those of water,” 
could have induced the supposition. This, then, is one of the 
defects incident to all the inventions of art, “ that though the 
radiating surface of the pipes does not imbibe or decompose the 
atmospheric moisture, it gives to it that buoyancy which causes a 
large quantity of it to escape through every crevice of the roof, 
and the remainder to be precipitated upon every object in contact 
with it, of a lower degree of temperature than itself.” And for 
this loss no compensating medium is provided in the construction 
of the apparatus. Connected with this negative imperfection is 
another of almost as much consequence, which in my opinion has 
not attracted the attention it deserves ; namely, no means are 
provided for counteracting the mischievous effects produced by 
the admission of cold air when ventilation is employed. There 
can be no doubt that an undue importance has been, to a great 
extent, attached to ventilation ; and the sickly, etiolated, appear¬ 
ance of stove plants in winter, instead of being attributable to a 
close atmosphere, might, with much more reason, be ascribed to 
a higher degree of temperature, and an insufficiency of light. 
But still, in most houses, ventilation is necessary ; and to have the 
means is requisite in all, if it be only to expel gaseous and vapor¬ 
ous impurities. It is, however, an error to suppose that the air 
admitted by ventilation, passes through that which is escaping, 
and so becomes partially heated before it reaches the plants ; this 
cannot be the case ; because, while the house is closed, the dilata¬ 
tion of air produced by an elevated temperature is resisted by 
compression, and its elastic force is increased ; so that, when a 
top light is let down (which is the usual m6de of ventilating in 
cold weather) the whole aperture is filled by the heated air 
escaping, until its pressure is reduced below that of the external 
atmosphere, when the latter immediately enters, and by its superior 
gravity falls to the bottom of the house, rapidly increasing in 
volume, till the whole of the former is driven off. Thus, in a few 
minutes, the plants are subjected to a change of often more than 
twenty degrees of temperature ; and the time chosen for this is 
when the organs of every plant are impelled to activity by the 
sun’s rays. The consequence is, the sap brought to the surface 
of the leaves for decomposition and elaboration, passes into vapour, 
and the heat required to dilate it is extracted from the plant. The 
warmth, too, which enabled the spongioles to perform their 
