STAGING, BEDS, ETC. 103 
Yet another way of surmounting this difficulty is to 
construct a long, shallow tank beneath the bed, with a 
brick and cement wall, or division, up the middle, and 
introduce the end of a flow pipe in one side, and the 
return in the other, both at the same end. A gap or break 
in the dividing wall is left at the far end, and when the 
tank and pipes are filled and the fire lit, the water circulates 
freely round the tank, in much the same manner as it 
would do through pipes. 
It is, however, found that in practice a dry bottom heat 
answers for most purposes almost if not quite as well as 
a moist one, and when a false bottom of an impervious 
nature, such as iron or slate, is employed, it is obvious 
that no moisture can ascend into the bed of fibre, etc, 
above, except perhaps to a very small extent through the 
laps or joints. With a porous material, such as perforated 
iron or zinc, kiln tiles, or the like, the case is different, 
but these materials are for the most part of a perishable 
nature, and for other reasons are unnecessary also, 
with perhaps a few exceptions. In all such work (propaga- 
ing, etc.) water must be given freely from above, and 
the cocoanut fibre must be kept constantly moist, or 1b loses 
its conductive power. 
In a hot-bed of this kind the pipes should be placed side 
by side—horizontally—and not one above the other. They 
ought also to be as equally distributed as possible, as shown 
in the sketch, where, in a pit 4ft. wide, the pipes are placed 
at about I1ft. distance from the front and back walls 
respectively. Ifa strong bottom heat is required, three 
rows of 4in. piping should be placed in a pit of this width; 
and in extreme cases four rows will not be found too much. 
