VENTILATION. 



11 



here described, in cases where grapes have to be forced 

 early. If the vines are not started till the beginning 

 of March they will do perfectly well without it, as is 

 evident from everyday experience. 



VENTILATION. 



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

 early forcing, one of considerable difficulty ; for it not 

 unfrequently happens that, after a severe frost at night, 

 requiring hot pipes, the sun breaks forth in the morn- 

 ing and raises the temperature of the vinery beyond a 

 safe point, while at the same time the wind may be 

 piercingly cold. In such circumstances there is no 

 alternative 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 open- 

 ing, and over this frame to tack a sheet of perforated 

 zinc, or a double piece of Hawthorn's hexagonal net- 

 ting. 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 



