56 STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 



ture as we would recommend that is, if a lean-to house was 

 desired by the erector, or the position would not admit of any 

 other kind. We need hardly mention that houses of this kind 

 are suitable in many positions where curvilinear houses would 

 be inappropriate, and where span-roofed houses would be 

 impracticable. This house is at once cheap and substantial, 

 in every way adapted for grape-growing, and presenting as 

 good an appearance to the spectator as one that would cost 

 double the sum, without any corresponding advantage. 



Fig. 16 is a span-roofed house on the same scale and the 

 same design. Of course, span-roofed houses are to be preferred, 

 either for plant-houses or for cold vineries, to lean-to houses, 

 although, as we have said, there are positions which render 

 lean-to houses preferable, even as cold houses. Span-roofed 

 houses cost somewhat more in their erection than single roofs ; 

 nevertheless, we consider it a matter of economy to erect a 

 span-roofed house where the position is suitable, because the 

 difference of cost is not so much as the difference of glass sur- 

 face available for the growth of vines. In fact, a span-roofed 

 house gives just two single-roofed houses of the dimensions of 

 one of its sides. Hence, it is clear, that as many grapes can be 

 grown in a span-roofed house, 50 feet long and 20 feet wide, as 

 in a single-roofed house, 100 feet long and 10 feet wide, while 

 the back wall, 100 feet in length, is saved. 



From the principles we have laid down for the construction 

 of hot-houses, in the beginning of this section, it will be apparent 

 that double-roofed houses are in every way superior to single 

 ones for the general purposes of horticulture, not only on account 

 of their superior lightness, but also as regards cost of erection. 

 And we find this fact is now becoming generally admitted, from 

 the prevailing tendency to erect double-houses, all over the 

 country, where the advantages of double roofs are not sacrificed 

 to the desire of having a more imposing and extensive appear- 

 ance from a single point of view. 



Amongst the various forms of curvilinear houses lately brought 

 under our notice, is that of forming the roof of the segment of a 

 circle, which shall equal the width of the house, a principle 

 which we think is not generally recognized, nor do we think it 



