STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 59 



that kingdom ; and though the immense structure is avowedly 

 for the growth of palmaceous plants, still the objections that 

 might be urged against its modification as a palm-house might, 

 with equal propriety, be urged against its form as a fruit house,. 

 on a smaller scale. If there be any fault in its curvilinear con- 

 struction, the fault is augmented as the dimensions of the 

 structure are increased. 



The objections that have been urged against curvilinear 

 houses in England can have little application in this country, 

 whatever force they might have in the cloudy climate of North- 

 ern Europe. And we cannot help thinking that the arguments 

 against them have, in a great degree, promoted their adoption,, 

 on account of the inconsiderate manner in which their mode of 

 structure has been questioned. We think it clear, that any form 

 of curvilinear roof, from the common rectangle to the semi- 

 ellipse, or the acuminated semi-dome, not only admits of a larger 

 run of roof, but also a larger proportion of light, than any form 

 of straight-lined roof that can be adopted, excepting the polypro- 

 sopic roof, which, in fact, is nothing more than an approximation 

 to the curvilinear, or spherical roof, having the advantages of 

 the one, without the disadvantages of the other. 



Another remarkable property possessed by curvilinear roofs, 

 and not by straight-lined ones, is their power of reflection and 

 refraction, which, in the hot summers of our climate, is of much 

 more importance, in a horticultural point of view, than is gener- 

 ally supposed. Though the power of curved surfaces of reflect- 

 ing the rays of light be similar to that of plane surfaces, yet the 

 plane is so small on which the rays fall, that its position is changed 

 before its concentration can cause injury to the foliage on which 

 it falls. As the surfaces of curvilinear roofs are, or ought to be, 

 presented more obliquely to the sun's rays than straight-lined 

 roofs, the amount of refraction, in very hot weather, will be 

 greater in the former than in the latter case. The more ob- 

 liquely the ray falls on the medium of refraction, the greater the 

 amount refracted. 



The general form of curvilinear-roofed houses,, in this country, 

 is the common curvature already described, forming the segment 

 of an ellipse, the ends being upright as in straight-lined houses. 

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