CONSTRUCTION. 



32g 



that can only be settled on the spot. The form and aiTangement, how- 

 ever, may be more positively determined. 



" The original house appropriated to the growth of Orchideae, at Chats- 

 worth [as described by Mr. Paxton, in "Magazine of Botany," Vol. ii., 

 p. 150, and of which^the annexed sketch will afford some idea], is seventy- 



five feet long and twelve feet six inches wide. The walk is com- 

 posed of pieces of wood nailed to sleepers, and is three feet six inches 

 wide. The flues are inclosed in hot-air chambers, and the heat is 

 admitted into the house by means of sliding ventilators on each side of 

 the walk. 



" On the top of the hot-air chambers the plants are placed, as seen in 

 the accompanying section : the stones covering the chamber being always 

 warm, give a gentle heat to the roots of the plants placed on them. The 

 top of the air-chamber is two feet six inches above the level of the floor. 

 The house contains three leaden water cisterns; the two end ones 

 are three feet square, the centre one three feet wide by eight feet long, 

 and is occupied with aquatic plants. 



" There are four fire places on the common principle : the two end 

 ones pass into the front chamber, cross under the walk in the centre 

 of the house, pass along the back chamber, and empty themselves at each 

 end. The two fires in the back • wall pass once along the front of the 

 back chamber, and, crossing through the wall at each end of the house, 

 pass along the outside of the wall, and heating the back sheds, A, empty 

 themselves in the centre of the back wall of the house. 



The height of the back wall of the house is eleven feet sLx inches, and 

 that of the front two feet six inches ; on the top of the front wall is an 



