THE LADIES’ MAGAZINE OF GARDENING. 
281 
lead lining. The part of the tube within the trough rises perpendicularly, 
and ends a little above the level of the surface of the soil. The shorter 
Fig. 71. 
END SECTION OF THE GLASS-CASE FOR PLANTS. 
portion, which is without the bottom of the trough, is turned horizontally, 
and terminates* in a brass connecting screw, to which a corresponding 
screw of a small stopcock is attached : to this stopcock a second stopcock, 
previously inserted in the end or corner of a Mackintosh air-pillow, is to 
be screwed on. This air-bag should be of such dimensions that it may be 
concealed within the frame on which the soil-trough stands, in the hollow 
of which it may be supported by tapes or strings passed from side to side 
under the bag. At the time the bag is attached to the stopcock or the 
brass tube, the temperature of the air in the conservatory should be 
observed ; and if it be at or near its maximum of elevation (and the air 
consequently near its maximum of dilatation), the bag should be nearly full 
of air ; and vice versa , if the temperature be low, the bag should be very 
flaccid when attached, in order that it may have capacity to receive the 
air expelled from the case when dilatation takes place on the temperature 
being raised. By this means the air contained within the case and 
bag, though constantly changing place, will never communicate with the 
external air, and its identity will be maintained with considerable 
exactness. 
