280 
indiscriminately, without rel’erence to the state of 
the air j for although the frame may become too 
hot in a clear sunny day, it will often happen that 
the air will be too severe for the plants. Under 
such circumstances it will be necessary, when the 
lights are propped up, for the purpose of mode- 
ratino- the heat in the frames, to hang over tlie 
opening canvas, garden mats, or some similar 
material, to prevent the sharp air or winds play- 
ing too powerfully upon the plants. Perhaps a 
more complete method would be to have a piece 
of fine wire-work fastened to the upper end of each 
light, and so contrived that when it is necessary to 
give air, it may serve the purpose of a prop, and at 
the same time be useful in tempering the air which 
enters the frame. I may further observe, that the 
common method of pushing the lights up and down 
alternately, for the purpose of giving air, should be 
abstained from, as in such cases, except the wea- 
ther is very still and mild, the plants would be 
more liable to be injured than if they were in the 
open air, owing to the strong draughts which the 
operation would produce. 
