GREENHOUSES. 



395 



Fig. 542. 



are intended to be of cast-iron, and the 

 top of polished pavement. The bearers 

 only in both cases should be let into 

 the wall, and the pave- 

 ment be kept at least 3 

 inches distant from it. 

 A much more simple and 

 economical form of sup- 

 port is an upright rod of 

 malleable iron 1 inch in 

 diameter, and a flat 

 wrought-iron arm or cross 

 bearer 3 inches broad and 

 1 inch thick welded to it : 

 these cross bearers to be 

 let into the wall and the 

 pavement laid upon them, 

 making the joints meet exactly over the 

 support. 



Ridge-and-furrow roofs for greenhouses 

 possess many of the merits of span-roofed 

 ones — such as admitting more light than 

 lean-to ones, and also from the position 

 of the astragals breaking the force of the 

 mid-day sun. One disadvantage pertains 

 even to ridge-and-furrow roofs, while 

 constructed on the lean-to principle, with 

 opaque back walls— namely, that little 

 more than one side of the plant is ex- 

 posed to the sun and air, just as occurs 

 under lean-to roofs of the ordinary con- 

 struction. It is better, therefore, in 

 adopting this form of roof, to have all the 

 sides of the structure of glass, to within a 

 few inches of the ground, and the roof 

 carried through of equal height from side 



to side. This was meant for Mr Duncan's 

 house, which has not been figured. Such 

 structures, admitting the maximum of 

 light to all sides of the plants alike, and 

 if not carried to too great a height, will 

 be found of all forms that best adapted for 

 growing fine specimens in. Having stated 

 this much, the reader will at once see the 

 necessity of abandoning the old and ab- 

 surd practice of placing plant-houses 

 against the face of solid walls, let the 

 aspect of that wall be to what point it may. 

 Hence it follows, that all plant-houses 

 should stand detached from all other build- 

 ings, and form of themselves entire and 

 complete structures, having the sides and 

 ends in all cases uniform. Conservatories 

 attached to the house or mansion should, 

 as far as the nature of the situation 

 will admit of, be of glass on all sides, 

 except that end at which they are joined 

 together. 



One of the first and most extensive houses 

 of this description was erected by Sir 

 Joseph Paxton at Chatsworth, of which the 

 annexed figures and letterpress descrip- 

 tion, taken from his "Magazine of Bo- 

 tany," vol. ii. p. 81, will give a clear idea. 

 This house " is so constructed that scarcely 

 any more light is obstructed than in a 

 metal-roofed house ; but it possesses, at 

 the same time, all the advantages of 

 wood. 



" Its whole length is 97-| feet, and its 

 breadth, from the back wall to the front 

 lights, 26 feet." Fig. 543 is a perspective 



Fig. 543. 



