112 GREENHOUSE CONSTRUCTION AND HEATING. 
occupants being attended to with water, etc., and a sudden 
change from a temperature of 60° or 70° to near freezing 
point is by no means conducive to the well being of the 
plants. This difficulty is however more formidable in 
theory than in practice, and by the exercise of a little 
I ay ENT 
care very little damage from this cause is usually 
experienced. This obstacle is also easily surmounted, at 
a slight extra cost, by constructing a pit at any rate with 
a deep but narrow sunk pathway, with a small door at 
one end, to-afford access to the interior, and enable tha 
