306 



FORCING GARDEN. 



of the flue. Along the upper side of this pipe are a num- 

 ber of small holes, becoming more frequent towards the 

 farther end, to allow the escape of steam : there are, be- 

 sides, a few perforations in the under side, to clear away 

 condensed water. The flue has a slight inclination to that 

 end of the house from which the water can be more easily 

 drained. 



Similar expedients were long ago employed in the heat- 

 ing of forcing-pits, by the late Mr. John Hay, of Edin- 

 burgh, a garden architect of great judgment and experi- 

 ence. Fig. 27 represents a recent variety of this mode of 



Fig. 27. 



supplying surface and bottom heat, by discharging steam 

 into flues and chambers filled with stones. The steam is 

 admitted by small pipes running along the central pit, in 

 channels about four inches deep, and of the same width. 

 These channels are crossed by others at right angles ; and 

 at the points of intersection the steam is permitted to 

 escape by two small holes, one on each side of the pipe. 



