SECTIONS AND DESCRIPTIONS OF HOTBED PITS. 
203 
In this, there is no iron pan for holding water under the bed, but a 
brick-work semicircular trough, lined with the best water-tight com¬ 
position. In this trough, which extends the whole length of the pit, 
a loop of two-inch hot-water pipe is laid, being fed from an elevated 
cistern above the boiler, as seen in the annexed sections. The purpose 
of the elevated cistern is to obtain another circulation of hot water to 
warm the air above the plants, when necessary, by pipes laid on breaks 
of the back and front walls, as shown in the section. 
Both the pipes are fed from the cistern, and return below into the 
boiler; and the cistern being above the level of circulation, accelerates 
the motion of the heated fluid. The water in the trough, through 
which the pipes in both plans are laid, is sufficiently heated to be 
constantly evolving steam, which, penetrating through the stage and 
body of earth, excites the plants into vigorous and healthy growth, 
and with far greater certainty and regularity than can, without much 
care and labour, be obtained from dung or any other fermenting 
material. 
The plan of working hotbeds by hot water has been yet but partially 
adopted; the scheme may be said to be yet in its infancy; but from 
the favourable results already reported of its efficiency, no doubt but 
improvements will be made in the heating apparatus, by increasing the 
capacity and powers of the boiler to answer many purposes at the 
same time. 
We shall recur to this subject on some future opportunity, or as 
soon as we have matured some ideas which are now floating loosely in 
our mind. * 
