440 The Principles of Fruit-growing. 



of the ground, this cold air may be drained into the 

 building by means of flues which are. laid through 

 the walls, the outer ends standing just above the 

 earth. Six -inch sewer pipes, at intervals about the 

 building, answer this purpose admirably. In a build- 

 ing thirty feet wide and seventy feet long, three of 

 these valves along either side, and one upon either 

 end, are probably sufficient for all ordinary require- 

 ments. Sub -ventilation is sometimes recommended, 

 and may often work to good advantage. This is 

 secured by running a long pipe from near the bottom 

 of a cellar storage out to the surface of the ground 

 six or more rods away. This pipe has a valve at 

 the outer end, or at least some protecting structure 

 to prevent the leaves and litter from blowing into 

 it, and it is ordinarily best, also, to have a valve 

 at the inner end. Inasmuch as the earth about this 

 subterranean passage is not frozen during the win- 

 ter, cold air may be drawn in from the outside 

 and be warmed up above the freezing point in its 

 passage through the tube. This type of ventilation 

 has been used with success in cellars designed for 

 the wintering of bees. It should always be remem- 

 bered that cold air contains less moisture than warm 

 air does. When very cold air is admitted, therefore, 

 moisture is rapidly taken up when its temperature 

 rises, and the cellar may be made too dry. It is 

 advisable, therefore, to raise the temperature of such 

 air to nearly its ultimate or required degree before 

 it enters the storage room. 



Cellars which are very dry cause the fruit to 



