CURVILINEAR ROOFS. 323 
mats, that he could keep out frost. With others, how- 
ever, the curvilinear form has given great satisfaction A 
considerable portion of the superior lightness of the cur- 
vilinear houses is due to the absence of rafters; and as 
these may also be dispensed with in plain roofs, the effect 
of these ought to be deducted in making a comparison. 
Perhaps, when everything else is rightly arranged, there is 
generally enough of light in common houses. Scarcely 
any species of fruit, when cultivated in the open air, is ex- 
posed during the whole day to the action of the solar rays, 
but must unavoidably be shaded at times by leaves and 
branches. It is difficult to suppose that, in respect to 
illumination, there is any remarkable deficiency in pits and 
glazed houses, in which have been ripened pine-apples and 
clusters of grapes, at least rivaling, if not surpassing, the 
produce of the most favored of their native climes. In 
the facility of admitting air, in the quantity and conveni- 
ence of trellises, and in other interior accommodations, it 
cannot be disputed that the old forms have rather the ad- 
vantage. : 
It has already been said that hot-house roofs of the com- 
mon kind are sometimes constructed without rafters or 
movable sashes. A considerable increase of light is thus 
obtained; but this benefit is attended with an almost in- 
superable defect, namely, the difficulty of producing a free 
and equable circulation of air. It is indeed probable that 
the common or plain-roofed hot-house will always continue 
the favorite form with practical gardeners, In it the raft- 
ers are arranged at equal distances, and are made of a deep 
and narrow form, with their under edges rounded off. 
Nicol recommends that they should be made two and one- 
fourth inches broad by ten inches deep. Perhaps they 
might be a little broader and shallower with advantage, 
