190 FIXED STRUCTURES FOR GROWING 



two curvilineal houses, 6, &, back sheds to these houses ; and c, lobby 

 common to both. These houses may be ventilated by openings in the upper 



Fig. 129. Grozifid plan of a curvilineal plant-house, with the entrance through a lobby in the back 



wall, 



part of the back wall, the orifice within being covered with pierced zinc, 

 and wooden shutters moving in grooves sympathetically. \Fhere a lobby 

 cannot conveniently be made in the back shed, one door may be made in the 

 centre of the front of each house, as at Messrs. Loddiges' ; and where the end 

 is semicircular, a door might be made in it in a similar manner, or with a 

 projection brought forward so as to form a porch : the mode represented in fig. 

 129 is, however, greatly preferable, as occasioning no obstruction to light. 



484. Ridge and furrow roofs. — Roofs formed in the ridge and furrow 

 manner, and even glass sashes so formed for pits, were tried by us many 

 years ago {Encyc. of Gard. 1st edit.) : and the idea has been improved on, 

 and applied in the happiest manner, by Mr. Paxton, at Chatsworth ; and 

 adopted by Mr. Marnock in the Sheffield Botanic Garden ; Jedediah Strutt, 

 Esq., at Belper; William Harrison, Esq., Cheshunt ; John Allcard, Esq., 

 Stratford- Green ; and at various other places. The advantages of this descrip- 

 tion of roof are : — 1. That the roof does not require to be raised so high 

 behind, in proportion to its width, as in flat roofs ; because the descent of the 

 water does not depend on the general slope of the roof, but on the slope oi 

 the ridges towards the furrows ; and the water in these furrows, being con- 

 fined to a narrow deep channel, and in a larger body than ever it can be on 

 the glass, passes along with proportionate rapidity. — 2. That the morning 

 and afternoon sun, by passing through the glass at right angles, produces 

 more light and heat at these times of the day, when they are, of course, 

 more wanted than at mid-day. — 3. The rays of the sun striking on the house 

 at an oblique angle at mid-day, the heat produced in the house at that 

 time is less intense than in houses of the ordinary kind, in which it is often 

 injurious, by rendering it necessary to admit large quantities of the external 

 air to lower the temperature. — 4. More light is admitted at all seasons, on 

 the principle that a bow window always admits more light to a room than 

 a straight window of the same width (283). — 5. The panes of glass, if crown 

 glass be employed, may be smaller than in houses the roofs of which are in 

 one plane, and yet, from there being a greater number of them, admit an 

 equal quantity of light ; from their smallness, also, they will cost less, 

 and be less liable to be broken by the freezing of water between the laps. 

 ■ — 6, By the employment of sheet window-glass, which is much thicker than 

 crown-glass, panes of three or four feet in length may be used, so that only 

 one pane need be requu-ed for each division, and consequently no lap being 

 required, no breakage by frost can take place, and no heated air can escape. 

 — And 7. That wind will have much less influence in cooling the roof, 

 because the sides of the ridges will be stieltered by their summits. Mr. 



