324 .. FORCING 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- 

 tains 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 



