242 
THE AMATEUR’S KITCHEN GARDEN. 
three feet. On each side of the walk beds must be formed by 
the erection of walls three feet in height and four and a half 
inches in thickness. 
In districts where a plentiful supply of leaves or other fer- 
menting materials can be obtained, hot-water pipes underneath 
the beds may be dispensed with, but where there is a likeli- 
hood of any difficulty in obtaining the fermenting materials, 
the plunge beds should have the pipes fixed underneath to 
maintain a sufficiency of bottom heat. In the arrangement 
of the heating apparatus a flow and return pipe should be 
fixed on each side close to the outer walls, and just above the 
level of the bed if there are no side lights ; and in houses 
provided with these the top pipe should be on a level with 
the wall plate. In addition to these a double row of piping 
on one side of the walk will be required. For houses not ex- 
ceeding ten feet wide three-inch pipes will be large enough, 
but for those of greater width, say twelve feet, four-inch pipes 
would be preferable. For bottom heat two rows of three-inch 
pipes underneath each bed will be requisite, — the flow and 
return to be nearly level, the flow being rather the highest, 
and to be fixed nine inches to the right and left of an 
imaginary line down the middle of the bed, and about four or 
five inches above the bottom. A platform nine inches or so 
above the top of the pipes will be required for the support of 
the fermenting materials, and this may be formed with slabs 
of stone or slate, sheets of galvanized iron or boards. If 
boards are used they must be placed an inch or so apart, to 
allow the heat from the pipes to pass readily through to the 
bed. 
The Plunge Bed. — Leaves gathered in a moderately dry 
condition form the most useful of all the fermenting materials 
for forcing ; they give off a moderate degree of warmth, and 
retain their heat for a considerable length of time ; conse- 
quently, there is no risk of the roots being burnt with an 
excess of heat, as is the case when stable manure is employed, 
neither does the necessity arise for frequently replenishing the 
beds for the maintenance of a proper degree of warmth. Tan 
is also suitable for the formation of plunge beds ; it heats 
steadily and retains its warmth for a very considerable period. 
Indeed, a tan bed may be kept in working condition for _ an 
indefinite period without the necessity arising for its being 
entirely remade. When the heat has declined below a certain 
