72 
OBSERVATIONS ON THE ROOFING OF HOT-HOUSES. 
sions come to by the calculators. But we know well that it was long 
ago suggested, that all forcing houses should have a roof facing three 
ways, viz., one graduated towards the east, to receive the morning sun, 
one towards the south, to intercept the mid-day, and another sloping 
to the west, to catch the setting beams. A modification of this scheme 
has been acted on ; and some beautiful conservatories "were so built 
fifty years ago. These buildings had glazed upright ends in the com¬ 
mon way, and next to the ends had five or six rafters and double 
lights laid also in the common way ; but from these points the back 
wall began to rise, and the front was carried outwards circularly; so 
that the middle of the building was swelled outwards and upwards, 
much more than the two ends. The exterior of these buildings was 
handsome, and the interior was convenient, in so far as that plants of all 
heights had ample space ; and the sides of the swell certainly admitted 
more both of the morning; and afternoon sun into the house. But the 
construction had defects : the lights which sloped laterally allowed 
every heavy shower to be thrown diagonally to the lower side, which 
either found its way through under the side of the sash, or was pre¬ 
cipitated with force over the front gutter. Another thing, the centre 
lights were so large and heavy, that, though counterpoised by cast-iron 
weights behind, they were always a great plague to be let down, 
or be got up. 
This plan was only an approach to the curvilinear roofs, which soon 
afterward came into fashion, and as erected at Messrs. Loddiges’, and 
many other places. Light, that grand and indispensable agent in the 
development and maturation of vegetable productions, was deemed 
everything for plants shut up in buildings; and hence the rejection of 
clumsy wooden rafters and sash-bars, and the substitution of those of 
cast-iron. Here perhaps the lover of new symmetrical forms, and the 
iron-founder together, got the better of the plain common sense of the 
gardener (ourselves among the rest), who knew well that without 
light no plant can thrive; but also knew that there may be excess of 
light, and particularly between the hours of eleven and three in the 
afternoon, of cloudless days; so that any part of the structure, which 
mitigates the sun’s ardour during these hours, is an advantage rather 
than otherwise. Still it must be confessed, that a good thing may be 
refused, but which cannot be commanded; a single mat, or an awning 
of thin canvas, may qualify the sun’s light and heat (for we cannot 
well have the first without the second also), but by no means can we gain 
an intenser degree of light than the face of the sky happens to give us. 
And if therefore a house be constructed to admit at all times the great¬ 
est volume of light, it is well, provided there is at the same time 
