320 



FORCING GARDEN. 



The boiler is of an oblong shape, measuring eleven feet 

 by four, and is formed of malleable iron. In certain 

 narrow houses intended by Messrs. Loddiges for green- 

 house plants, a single steam-pipe is found sufficient. In 

 other houses of considerable height and breadth, or 

 where a higher temperature is required, as in the palm- 

 house, the steam-flue is made to describe two or three 

 turns. 



Water, contained in large vessels or pipes, is some- 

 times heated by steam, and so made the medium of 

 conveying caloric to the atmosphere of glazed houses. 

 The annexed figure represents an example of this ar- 



Fig. 24. 



rangement. In the instance here given, a small steam- 

 tube, one inch in diameter, enters a water-pipe eight 

 inches in diameter, and twenty-eight feet long, wholly 

 within the forcing-house ; it passes into the large pipe 

 at the centre, and after traversing its whole length and 

 returning, it issues out immediately below the point at 

 which it entered. It then forms a siphon, by which the 

 condensed water is conveyed away. A more detailed 

 description may be found in the London Sorticultural 

 Transactions^ vol. iii. 



Steam is sometimes employed to furnish bottom 

 heat. In the garden of Mr. Sturge, near Bath, a shal- 

 low cistern of water is heated by a steam-pipe, in the 



