THE MAKING OF HOT-BEDS. 131 



underneath ; about two feet from this inner brick-work there 

 is a four-inch wall, as it were, leaving an eighteen-inch 

 vacancy between that and the inner one all round. In this 

 vacancy is placed hot dung pressed dowTi close, the heat of 

 which goes through the holes in the sides of the chamber, 

 which is thus raised to a considerable temperature and forms 

 bottom heat, while the dung being heaped up outside to nearly 

 the top, adds to the temperature of the air w^ithin the pit. 

 This kind of pit or brick frame is built two feet under the 

 ground and two above ground, the outer wall being only built 

 up to the surface of the ground, and the dung being heaped 

 up to pretty near the top of the inner wall. The advantage 

 of these pits is, that the dung can be changed when it cools, 

 and new hot dung be put in its place as often or fast as we 

 please, without the risk of disturbing anything that is gTowing. 

 Another kind of dung-pit is constructed on pieces of brick- 

 work, to be hollow underneath, with only a bottom of thin 

 boards, and the hot dung is put between these brick piers, 

 filled in quite sohd, and with a goodly quantity of dung also 

 outside. This can be changed in the same way as often as the 

 temperature declines ; but although we have practised with 

 all these, there is nothing for simpUcity and economy that 

 beats the ordinary wooden frame and glass, as described at 

 first. In nurseries, where these are used in great plenty, the 

 ordinary size of the frame is, with lights, five feet six inches 

 from back to front, and three feet six inches wide, the back 

 of the frame being from twelve to eighteen inches high, and 

 the front from six to ten inches high, so that there is a little 

 slope naturally, if laid on a flat surface of dung, and the dung 

 may be laid sloping, so that there would be a still greater 

 slope, in fact, more or less, according to our fancy. In 

 private gardens, eighteen inches for the back and nine inches 

 for the front, is a good proportion, or as the cutting of the 

 boards to make them is generally managed to avoid waste, one 

 board high in front and two boards high behind is a very 

 good proportion. But according to the shallowness or the 

 height of the frame, so the wood is set down on the dung, or 

 set on part of the thickness of soil, because there ought 

 to be six inches of soil in the shallowest parts, and nine 

 inches in the centre, and if this were all inside the wood- 

 work, there would not be sufficient room between the soil 

 and the glass in a shallow frame. 



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