28 GREENHOUSE CONSTRUCTION AND HEATING. 
etc., will be found extremely suitable. An illustration of a 
fine example of orchid house is given in Fig. 67 (pp. 88, 89). 
With very few exceptions, greenhouses of all kinds should 
be erected, as far as possible, in open positions, @.¢., away 
from the shade of high trees, lofty buildings, or the like. 
Though in hot summer weather a little shade is often desir- 
able and even beneficial, as a rule, plants of all kinds under 
glass require all the free light and sunshine they can get in 
our none too sunny climate. Unless the plants receive plenty 
of free light on all sides, the growth of most descriptions is 
sure to be more or less weak and spindly, with an absence of 
that freedom of flowering that is so important a point in the 
growth of plants for market in pacticular. 
From what has been stated above, it will be seen that the 
chief points to be considered in the construction of glass- 
houses for various purposes are :— (1) Proportions ; (2) Pitch ; 
(8) Ventilation ; and (4) Temperature, or heating power. 
Proportion.—Aas regards the first, sufficient has already 
been said, probably, to show under what conditions, or for 
what purposes, large or spacious structures should be preterred 
to those of smaller proportions, and also the approximate 
widths, etc., usually adopted by the best growers for the 
different subjects. But beyond this, it may be as well te 
say here that houses of considerable dimensions possess 
certain advantages over smaller ones, and for many purposes 
are decidedly preterehle. For one thing, they do not become 
cool nearly so rapidly as small houses, at least when closed, 
and although under the influence of sun the temperature rises 
nearly or quite as rapidly, yet in hot or bright weather they 
do not become nearly so close and stuffy as smaller, lower 
structures, as the superheated air rises to the apex of the 
