350 FORCING GARDEN. 
Mr. M’Murtrie, and it will be understood by the section 
and plan given in the preceding figures. 
A shallow bark-béd, about two feet deep, rests upon 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 inclosed part of the flue, and of the steam in 
the chamber, an abundant and salubrious bottom-heat is 
easily maintained. 
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 culture. The 
heat arising from violent fermentation is greater than the 
tender roots can bear, and, if all watchfulness be not em- 
ployed, the labor of many months may be blasted in a 
singleday. Mr. Knight discarded bottom-heat altogether ; 
but he did not succeed in convincing others that pine- 
apples could be grown equally well without it. Bottom- 
heat is, however, very generally, kept too high. Perhaps 
the upper limit of its temperature may 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 tempera- 
ture is thus obtained. A far preferable method is to em- 
ploy a slow thermometer, slightly cased in wire, to protest 
it when pushed into the bed. 
