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. 
ed 8 
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ear 
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. 
