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. 



