THE CONSTRUCTION OF GRANARIES. 173 



should be about 3 ft., and the walls should be plain. A 

 tube in sheet iron or brass of about 4 in. in diameter or 

 more, covered by a larger tube, leaving a space between the 

 two intended to receive a current of vapour, is placed, ver- 

 tically, the height of the compartments of the granary, with 

 which it communicates by means of branch tubes, the ends 

 of which are partially open to the air. The air being dri- 

 ven through by a ventilator, becomes heated in passing, and 

 penetrates to the upper part of each stage, leaving by the 

 small tubes at each stage. This air, the temperature of 

 which may be more or less elevated, and which thus circu- 

 lates during the working of the apparatus, dries the grain 

 completely. The approaching of the floors in this modi- 

 fied system allows of two similar apparatuses being placed 

 one above the other, separated by a floor, the openings of 

 which may be shut by means of rods placed for the purpose, 

 so that when the two apparatuses are full, the openings of 

 the floor are shut. The lower apparatus may thus work 

 alone, and when its upper compartment is empty, communi- 

 cation may be re-established between the two by turning 

 the rods." 



