232 
GARDEN ARCHITECTURE. 
the house will be more regularly and effectually heated than if there was only one 
slope to the roof. 
That plants can be grown to greater perfection in a span-roofed house, and kept 
in a more healthy condition, with the least attention, is a matter of notoriety. Its 
lightness, and its thorough ventilation, are two of the main causes of its superiority ; 
and every gardener is aware that, for greenhouse plants at least, light and air are 
of vital, importance ; while for all exotics it is essential that the former should be 
fully at command, though it may be desirable at times to diminish its influence by 
artificial means. 
It has often been declared, that it is of little moment whether the hack w T all and 
ends of a house facing the south be glazed or not, provided the slope of the front 
roof be such as to receive the direct rays of the sun during the greater part of the 
year. This fallacy is completely refuted by modern experience, which attests that 
the more thoroughly exotic plants are surrounded by materials which admit light 
freely, the more nearly does their state approximate to that of nature, and the more 
dwarf, dense, and robust are their developments. Indeed, we may mention that 
though the old notion of gardeners, that high houses are most improper for plants, 
is correct when applied to those which have one or more of their walls opaque, and 
composed of bricks or masonry ; yet if every portion of the roof be glazed to within 
a few feet of the ground, it has been found that the attenuating and etiolating effects 
of which cultivators formerly had to complain in lofty erections, have not been 
experienced, and the plants grow as strongly, and remain as compact in their habit, 
as if they w~ere merely a few feet from the glass. 
In houses of this description, such is the power of solar agency, that a difficulty 
of quite another nature has to be encountered ; for the rays of light and heat being 
transmitted so perfectly, render the protection of the roots of potted plants almost 
indispensable. Still it is important to observe that the atmosphere does not, as some 
have supposed, become heated to an uncomfortable degree ; because the solar rays, 
having no solid or massive substance to act upon, (as in the case of houses with brick 
walls at the back,) are but slightly refracted by the glass, and pass through the 
house rather than concentrate themselves within it. Hence, a house glazed on all 
sides, if adequately ventilated, will really be cooler in the summer than one which 
has a single glass slope with a southern aspect and an opaque hack wall. 
Not wishing to dogmatize on any subject, especially on one of such consequence 
as that of building plant-houses, we will strive to meet the objections that have 
been or may be urged against having two glass slopes to a roof. It appears to us, 
however, that these may all be ranged under the single head of economy ; and as 
we think this a matter of considerable interest, we shall attempt to show that the 
economical argument has exceedingly little to substantiate it : whereas, when 
weighed against the immense benefits conferred by the other system, the question 
assumes quite a contrary aspect, and the saving is clearly on the side we advocate. 
Many false views are current respecting the nature of true economy in the 
