304 FORCING GARDEN. 
paratus exist at Syon House, the princely seat of the Duke 
of Northumberland, near Brentford, and in the nursery 
garden of Messrs. Loddiges at Hackney. At the latter 
place, glazed houses, to the extent of almost a thousand 
feet in length, and forming three sides of a square, are 
heated solely by steam from one boiler. The boiler is of 
an oblong shape, measuring eleven feet by four, and is 
formed of malleable iron. In certain narrow houses in- 
tended by Messrs. Loddiges for green-house plants, a sin- 
gle steam-pipe is found sufficient. In other houses of con- 
siderable height and breadth, or where a higher tempera- 
ture 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 sometimes 
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 arrangement. 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 con- 
