EVAPORATION OF FPOJITS. 



11 



windows, and other openings are the same size and the interior 

 dimensions of the kiln are the same. 



Roof and ventilators. — The roof is always of frame construction, 

 consisting of 2 by 6 inch rafters spaced 24 inches apart and covered 

 w T ith sheathing and an asphaltum roofing paper. Metal roofing is 

 not well adapted to kilns, as the sulphur fumes used in bleaching the 

 apples soon corrode the metal. The method of constructing the roof 

 is shown in Figure 1. The type of ventilator used on practically all 

 modern kilns is shown in the same figure. The ventilators are always 

 placed at the peak of the roof, so that the moisture-laden air will be 

 quickly removed. This type of ventilator has been found to be wind 

 and rain proof. No matter which way the wind blows the kiln is 

 sure to draw. The wind passes through the opening between the 

 roof and the outside wall of the ventilator and causes suction, which 

 tends to create a draft from the interior of the kiln. Rain on the 



1 



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Fig. 2. — Drying plant at Victor, N. Y., equipped with modern ventilators. 



roof of the ventilator falls between. the outside and inside walls of 

 the ventilator, strikes the main roof, and runs off. Figure 2 shows 

 a drying plant equipped with ventilators of this type. Other styles 

 of ventilators are used, but are not as efficient as the type just 

 described. 



Heating apparatus. — Cast-iron, hard-coal furnaces are universally 

 used in apple kilns throughout the Eastern States. These furnaces 

 have a grate of 5 to 8 square feet and are capable of supplying heat 

 for a standard 20 by 20 foot kiln. Such furnaces are of very heavy 

 construction, weighing 1,500 to 1,800 pounds, and consequently they 

 maintain a fairly uniform temperature with only occasional attention 

 from the fireman. The products of combustion pass through sheet- 

 iron pipes arranged in rows under the floor and finally into the chim- 

 ney. Three systems of piping are in use, all of which are illustrated 

 in Figure 3. The difference in these systems consists in the extent 



