216 GREENHOUSE CONSTRUCTION AND HEATING. 
down by pumping, in the meantime), to sink, bodily, 
a galvanized iron tank sufficiently large to contain the 
boiler, or boilers, and allow room for stoking. This 
(which need not, of course, be much deeper than the 
extreme height to which the water is likely to rise), must 
be weighted down in some way, if there is much water, 
but by the time the boiler and brickwork are in place it 
will be steady enough, and where the upper edge is below 
the surface the sides should be carried up with good brick 
and cement work to the ground level, or rather above. 
Such a tank should, if possible, have a concrete bed to 
' rest on, and also be filled in all round the sides with nearly 
or quite a foot of concrete. 
But although appearing sufficiently feasible and even 
easy on paper, there are some serious objections to this 
method of excluding the water. In the first place tanks 
of such a large size are rather costly, running into £40 
or £50 apiece if of only moderately large dimensions. Then, 
when down, the bottom frequently ‘‘buckles’’ badly, 
and I have seen cases where though level enough when 
first fixed, by the time the boilers and setting were got 
in, the brickwork and furnace fittings were terribly out 
of square through the bottom having given way to some 
extent. Lastly, a very few years’ wear, with heavy nailed 
boots, coke, ashes, etc., suffices to wear holes through 
the bottom where the stoker stands, besides which rust 
and decay are never idle, and in fact the metal. soon 
gives way and lets in the water once more. 
Now a good brick and cement hole may be somewhat 
more troublesome and possibly expensive in the first place, 
but once well constructed it will last for a life-time, if not 
