VENTILATION. 



This is a point of great importance, and, in very early 

 forcing, one of considerable difficulty; for it not unfre- 

 quently happens that, after a severe frost at night, re- 

 quiring hot pipes, the sun breaks forth in the morning, 

 and raises the temperature of the vinery beyond a safe 

 point, while at the same time the wind may be pierc- 

 ingly cold. In such circumstances there is no alterna- 

 tive but to open the top ventilators, when the hot air 

 will rush out ; but at the same time another current 

 will rush into the house, of air too cold to be admitted 

 amongst the tender foliage of the vine with safety. 

 To modify this evil, it is a good plan to have a light 

 wooden frame made to fit the ventilating opening, and 

 over this frame to tack a sheet of perforated zinc, or 

 a double piece of Hawthorn's hexagonal netting. This 

 will break up the rush of air into a great many small 

 streams that will more readily mingle with the hot 

 air of the house, and get so far heated before it reaches 

 the foliage. 



It would be no safer to admit the cold air by the 

 front ventilating-sashes to take the place of that mak- 

 ing its exit by the top ones, unless some means were 

 employed to take the chill off it before it is discharged 

 into the body of the house. For this purpose I have 

 designed what I have termed "The Hot- Air Ventilator" 

 (fig. 5). This apparatus consists of a sheath of copper 

 placed over a row of the front pipes. The diameter of 

 this sheath is one inch more than the hot pipe it en- 

 closes, consequently there is an open space of half an 



