GREENHOUSES. 



387 



be set ; c c the sides, fitted up with a ser- 

 pentine table on each side. By such an 

 arrangement a greater surface of foliage 

 will be exposed to the sun and light, and 

 the plants brought not only into better 

 view, but they will be within reach from, 

 the passage, both on the centre and side 

 tables. Such an arrangement will be 

 found exceedingly well adapted for a green- 

 house or heathery, where the plants are 

 kept small. 



In regard to elevation, fig. 526, the 



Fig. 526. 



superstructure stands on a plinth or 

 basement of ashlar stone, 6 or 8 inches 

 high. From the curvilinear shape of the 

 roof, such a house should be metallic ; the 

 pilasters and wall-plates (the latter also 

 serving for a gutter) should be of cast- 

 iron ; the frames of the doors (for the 

 ends and front are a continuation of fold- 

 ing doors, or what is in general called 

 French windows) may be of wrought 

 iron, the astragals of copper, and those 

 of the roof at least of wrought iron. 

 Although the roof of such a house must 

 be of metallic material, on account of 

 the curvature at the lower ends of the 

 astragals, there would be no objection to 

 the front doors being entirely of wood, 

 as they would be lighter, and open 

 and shut with greater ease ; or the top 

 and bottom rails and side stiles may be 

 of wood, and the astragals of hollow cop- 

 per sash-bar. It may be held as a pretty 

 general rule, that all doors and movable 

 sashes should be of wood, or at least 

 wood and copper, as iron ones are too 

 heavy to be safely or conveniently moved. 

 The pilasters, however, in the case before 

 us, between the doors, should be 6 inches 

 square, of cast-iron, with neat mouldings 



on both faces, and may be cast hollow, 

 with equal strength and considerable 

 economy, if the sashes are to open by 

 running past each other upon a rail fixed 

 to the plinth, and a groove in the lintel, 

 which is of all plans the best ; but if they 

 are to be hung by hinges at their sides, 

 some, difficulty will arise in giving the 

 screws a proper hold, if the pilasters 

 are hollow. Perhaps the simplest way 

 will be, to let the screws pass right 

 through the pilaster, and to counter-sink 

 the nuts on the op- 

 posite side. If the 

 doors are of wood, 

 or wood and copper 

 bars, and run on a 

 rail, they may be all 

 in one piece, namely 

 4 feet wide; but if 

 of metal, they should 

 be in two pieces of 

 half that size. 



The astragals of the 

 roof should be kept in 

 their places by two 

 straining-rods of iron, 

 to which each astragal 

 should be screwed. The roof water may be 

 conveyed down as in the last example, and 

 the heating be upon the same principle ; — 

 only, in so far as this house has a back 

 wall of brick or stone, the furnace may 

 be of the usual form and in the usual 

 position, and the smoke may be carried 

 off as shown in the figure. Ventilation 

 is effected by opening any or all of the 

 front or end doors, and by openings in 

 the back wall near the top, which will 

 require to be large, say 4 feet in length 

 by 1 foot in depth of a clear opening. 



An improvement on such a house as 

 this would be the removal of the back 

 wall, and the construction of a similar 

 roof behind, bringing the tops of the two 

 roofs to within 9 inches of each other, and 

 securing ventilation as shown in the case 

 of wooden houses in section Ventila- 

 tion. 



The roof of such a house is without 

 rafters or framed sashes, and simply con- 

 sists of a continuation of astragals placed 

 at equal distances, that distance being 

 governed by the breadth of the glass 

 intended to be used. We think 9 inches 

 a good breadth for the glass of such 

 roofs; and for the flatter part, towards 



