368 FORcma garden. 



an arched chamber of single brick. 1 is the fire-place; 

 2, a; fire-flue running along the whole length- of the 

 chamber 4, which is also kept full of steam by means 

 of the boiler and pipe 3; the aperture 5 admits steam 

 and heat into the air of the pit, and of these there is 

 one, both in back and front, under each sash, capable 

 of being stopped at pleasure. The waste--pipe 6 allows 

 the steam to escape, when the apertures marked 5 are 

 shut. By the return of the flue 2, the atmosphere of 

 the house is heated; and by the joint action of the in- 

 closed part of the flue, and of the steam in the chamber, 

 an abundant and salubrious bottom-heat is easily main- 

 tained. 



The proper management of bottom-heat is a matter 

 of some difficulty, and in this there have been more 

 failures than in any other part of the pine-apple cul- 

 ture. The heat arising from violent fermentation is 

 greater than the tender roots can bear, and, if all 

 watchfulness be not employed, the labor of many 

 months may be blasted in a single day. Mr, Knight 

 discarded bottom-heat altogether; but he did not suc- 

 ceed in convincing others that pine-appleS could be 

 grown equally well without it. Bottom-heat is, how- 

 ever, very generally, kept too high. Perhaps the 

 upper limit of its temperature rnay be fixed at blood- 

 heat, or at most 100°, while the under or winter limit 

 may be brought down to 70° or 75°. Gardeners are 

 accustomed to judge of the heat of the bed by means of 

 long sticks pushed into it; these are occasionally drawn 

 out and felt by the hand, and a rough guess at the 

 temperature is thus obtained. A far preferable me- 

 thod is to employ a slow thermometer, slightly cased 

 in wire, to protect it when pushed into the bed. 



