324 FORUING GARDEN. 
The size of the sashes may depend on the magnitude of 
the house; their breadth, however, should range from three 
and a half to four feet. Except in very large houses, 
sashes are always disposed in two tiers, the upper row 
sliding down over the under one. Where there are venti- 
lators in the front wall or upright glass, the sashes in the 
upper tier alone require to be movable, and, for the sake 
of convenience, they should be made considerably shorter 
than the others. They are furnished with cords, pulleys, 
rollers, and weights, though the last, with no very prudent 
regard to economy, are sometimes omitted. Formerly, all 
hot-houses were constructed with upright sashes in front. 
One of the most eminent garden architects of the present 
day, (Mr. Atkinson,) has discontinued the practice; and, 
except in ornamental structures, it is hard to say why it 
should not be laid aside altogether: for while upright 
sashes certainly tend to weaken the fabric, and increase its 
expense, their utility is at least problematical. 
Glass is the transparent material universally employed, 
for it is at once a ready transmitter of the rays of the sun, 
and a bad conductor of caloric, or it admits light, and re- 
taius the heat generated by flues. That some tint of blue 
or green would lessen the scorching effects of the rays 
seems generally admitted ; but the precise tint has not yet 
been satisfactorily established. Formerly the panes of 
glass employed were of large size, but small panes are 
found. to be more economical, being less liable to break, 
and more easily replaced. It is believed that a pane seven 
inches in breadth by six in length is the cheapest form in 
which good glass can be obtained. In glazing, it is im- 
portant to keep the overlaps of the panes of small dimen- 
sions, perhaps from one-fourth to one-eighth of an inch in 
breadth. This diminishes the breakage which arises from 
