598 



Journal of Agriculture, Victoria. [10 Oct., 1917. 



Tlie roof of the building is so constructed that the apex or ridgepole 

 is directly over the middle of the row of kilns, which are ceiled directly 

 on the rafters with metal or boards. The ventilating shaft occupies 

 the apex of the roof, extends the entire length of the building, and 

 should be 3 feet in width and at least 4 feet in height. A rather widely 

 used type of ventilator is shown in Figure IV. Its distinctive feature 

 is the fact that it is double-walled, the outer walls liaving no connexion 

 with the inner, and being placed at a distance of 12 to 16 inches from 

 them. These outer walls are not covered by the roof of the ventilator, 

 but are boarded solidly except for a space of 12 inches in width at the 



Fig. IV — Details of construction of double-walled ventilator. Warm air 

 escapes from the shaft through the continuous opening 12 inches in width at 

 the top of the inner wall; the opening at the bottom of the outer wall permits 

 cold air to enter and pass up between the walls, assisting the draught, while 

 the upper portion of the outer wall keeps snow or rain from blowing into the 

 shaft. 



bottom, which is left open for the entire length. The inner walls are 

 boarded up solidly from the bottom for a distance of 3 feet, leaving a 

 Sipace a foot in width just beneath the ventilator roof, through which the 

 waiin air escapes from the kilns. The outer wall thus has an opening 

 at the bottom through which currents of cold air moving along the roof 

 of the building may enter the space between the walls, passing up be- 

 tween them and assisting in carrying off the wann moist air escaping 

 at the top of the shaft. The outer wall makes it impossible for the wind 

 to blow directly into the opening in the inner wall, which would inter- 

 fere with the escape of the warm air, and also keej^s rain or snow from 



