ON THE AERIAL SYSTEM OF FORCING. 
155 
;o shadow, and a very much improved mode of heating, which has only borrowed 
L name, while it retains little of the substance, has, in some two or three instances, 
en adopted by men of discerning intellect, to the great improvement of the pro* 
3 tive and forcing departments of horticulture. 
A very fair approximation to an uniformity of heat through an entire house — 
th a very great increase of generally diffusable temperature, if desirable, and at 
mmand — has been attained. Our direct observations led to the publication of that 
tide (Page 70, No. 160) on an erection which comprised a vinery and cooler depart- 
ent. This machinery acted so well, that, while admitting defects, we can con- 
ientiously recommend it to those who intend to erect one or two small houses upon 
Ifidly economised outlay : it should seem almost impossible to erect a greenhouse 
)on more safe and efficient principles, especially if, in lieu of sliding, or even 
ovable front sashes, there be a number of external ventilating holes at the ground 
vel, or even rather below it, made in the front, back, and end walls for the admis- 
on of air from without : all or any of these may be left open, or be closed, as 
rcumstances indicate ; but it is certain that air so admitted will never, even in the 
)ldest weather, produce the comparative injury to plants which a blast dashing from 
le top, or even by front and end sashes invariably causes. 
The great principle before-named, first inculcated by Dalton, that each gas acts 
3 a vacuum to every other gas, ought always to regulate the operations of all who 
rect plant-houses. It is this principle which forms the basis of the modified Pol- 
laise system; and it, or any of its improved forms, must be made to conform to 
hat principle. 
There are few persons, in this day of philosophical mechanism, who have been 
aore assailed by rude aspersions than Mr. Meek, of Nutfield, in Surrey. Had 
hat enthusiastic, high-minded gentleman, avoided the name of Polmaise — had he 
imply and philosophically announced his own conceptions, now carried into full 
effect, he would have been welcomed as an able exemplifier of scientific structures, 
lie shall speak for himself in the following extract from the Journal of the Horti- 
ultural Society : — 
“ The philosopher tells us there is a form of matter which diffuses heat with a 
! apidity unknown to any other ; and, moreover, this very instrument of diffusion is 
he object itself which we seek to heat ; thus, instead of employing a go-between, we 
leat that, at once, which it is our object to heat. We desire to heat a certain amount 
)f air ; we provide the heat ; the air appropriates and diffuses it with an equality 
md speed which evidently cannot be attained by any other means. Is it any wonder, 
hat a plan based on principles so natural and so philosophical, should be eminently 
successful ? that it should be cheap, as compared to any other means, in its first 
cost, and economical in its use? For the expense of diffusion is saved. What 
necessity exists of carrying heat to the air, when the air will travel to the heat? 
What need of boilers, cisterns, stopcocks, pipes, and water, to produce and diffuse 
atmospheric heat ? Is it not certain that such means must involve waste in cost, 
