160 DISEASES OF GLASSHOUSE PLANTS 
bent like the handle of a plasterer’s trowel placed on the 
opposite side to the laterals serves to connect the grid 
to a length of 14-inch best flexible hose piping fitted to 
the main 2-inch steam barrel leading to the boiler. <A 
trench 30 inches wide, 6 feet long, and 16 inches deep is 
made and the soil wheeled away to the other end of the 
bed to be sterilized. The grid is placed in the 
bottom of the trench and a second trench is dug similar 
to the first, and immediately behind it. The soil from 
this trench is thrown into the first and covers the grid. 
When the trench has been filled, a tarpaulin is thrown 
over the top and steam passed for 10 to 15 minutes. The 
grid is then pulled out and back into the empty trench, 
which is filled up and steamed as was the first. By 
working a pair of these grids one man can be fully 
employed. 
The success of this method of steaming depends very 
considerably upon keeping the pipes and grid free 
from condensation water. Any quantity of water lodging 
in the pipes will cause failure by checking the proper flow 
of the steam. The holes in the laterals, being placed 
low down near the soil, prevent any condensation water 
from filling the pipe, and the end hole, being made at the 
bottom of the tube, allows the water to drain away. When 
the actual steaming is done some distance away from the 
boiler, and consequently a considerable length of 2-inch 
steam barrel has to be used, there is a tendency for con- 
densation water to lodge in the pipes. This is overcome 
by placing a steam trap at the end of the steam barrel 
just in front of the T-piece connected to the hoses. 
In the absence of a steam trap a valve slightly opened 
can be fitted as shown at Fig. 42 (e). This allows the 
condensation water to drain away, but does not affect 
appreciably the steam pressure. 
(c) ‘ Tray’? Method.—In this method the soil is well 
dug one spit deep, so as to assist the penetration of the 
steam, and it is important that the soil should be moder- 
