94 
THE FLORIST AND POMOLOGIST. 
Leaving the subject of construction, I will now just glance at that of venti¬ 
lation, the proper arrangement for which is of the first importance in the con¬ 
struction of houses. The great objects of ventilation are, first, a pure and healthy 
atmosphere, and, secondly, an equable temperature. To secure these objects 
there seems to be no plan so suitable as that at present most generally in use, 
and which is also most in accordance with our knowledge of atmospheric action; 
and that consists in providing for the admission of external air at the lower part 
of the house, and for its escape at the upper part after it has done its work, and 
has supplied to vegetable life those great requisites that pure air alone can give. 
In all correct modes of ventilation the possibility of a continuous draught will 
be avoided, and if the proportion of top air given is about one-fourth of that at 
the bottom there is no doubt that this object will be perfectly secured. It is 
not possible to lay down any rule of ventilation that will suit all descriptions of 
plants and fruits alike, for all gardeners know that whilst some plants will 
exist and be healthy in a freely ventilated and dry atmosphere, others require 
a humid and confined one : but in every case the practical knowledge of the 
gardener will prove his safest and surest guide. The application to bottom 
ventilation of the crank principle which admits of a simultaneous and instant com¬ 
mand over the amount of air, is a great improvement; and when this system 
is applied to houses both at top and bottom, it seems to be as nearly as possible 
the most perfect mode of ventilating glass structures. 
With regard to modes of heating, it does not appear necessary to discuss any 
other than that most generally adopted, in which hot water is made the medium 
of conveying heat. Brick fiues have done good service, but are going out of 
use. Hot water will perform whatever is required of it, provided only there be 
plenty of boiler power and sufficient piping for its free circulation. The 
quantity of piping necessary for heating houses must depend on their size, and 
the purposes they are intended to serve. Forcing-houses and stoves necessarily 
require a greater proportion of heating power than greenhouses, or those 
intended for plants of a half-hardy character; but I think I shall not be far 
wrong if I put the quantity of four-inch piping necessary to heat a thousand 
cubic feet of air in an ordinary greenhouse at about 60 feet; but to beat the 
same quantity in a stove or forcing-house not less than 150 feet would be 
required. 
With regard to the relative merits of the various kinds of boilers now in 
use, I could hardly express any decided opinion. The most important features 
of any boiler are cheapness, durability, great heating power, and the least 
possible consumption of fuel to produce the greatest effect. The question of 
setting boilers in brickwork or not may also be left open; still my predilections 
at present are in favour of a boiler being permanently set, encasing it with a 
considerable body of brickwork, for I believe that by this means the rapid loss 
of heat that otherwise takes place when the fire becomes low is arrested, and 
that the warmth is retained for a considerably longer period. 
Maybush , Shirley , Southampton. Alexander Dean. 
PENTSTEMONS. 
These are among the most showy and charming of herbaceous plants, and 
well deserve a place in every collection. Some kinds are truly herbaceous, 
dying down to the ground annually; whilst others are more or less shrubby. 
They thrive and flourish well in any good garden soil, with a little peat or leaf 
soil mixed with it. Some of the kinds are well adapted for ribbon-borders, and 
all for mixed borders. 
