EVAPORATION OF FRUITS. 13 



to keep free from soot. In the Pacific Coast States and in parts of 

 the South the absence of supplies of hard coal makes the use of other 

 fuel necessary. Wood is generally used. The furnaces employed 

 are usually heavy stoves of the box type, fitted with special linings, 

 although brick or stone furnaces lined with fire brick and covered 

 with heavy sheet-iron tops are also successfully used. When wood 

 is the fuel used, especial care must be taken to keep all joints of 

 piping and furnace tight, as the volatile resins of the wood may other- 

 wise impart a disagreeable flavor to the fruit. It is impracticable to 

 use soft coal, on account of the soot and smoke. 



Chimneys. — As it is the practice to build the kilns in rows, it is the 

 usual custom to build a 2-flue chimney in the- wall between two kilns 

 to serve both furnaces. The chimneys have two 8 by 10 inch flues 

 and must be carried above the highest part of the building, so there 

 will be a good draft. Near-by trees which are higher than the build- 

 ing may cause much difficulty in securing a good draft, and this point 

 should be borne in mind in determining the location of the plant. 



Distributing hopper and air ducts. — Drying in these kilns depends 

 on passing heated air through the material which is spread on the 

 drying floor. It is necessary to have suitable openings, so that cold 

 air can be admitted at the bottom of the kiln, be heated by being 

 passed over the furnace and its piping, and, after passing through the 

 material to be dried, discharged through the ventilators at the top 

 of the building. The sizes and location of the ducts for the inlet of 

 the air are shown in Figure 1. These ducts are 1^ feet high by 5 feet 

 long, and are four in number, two on each side of the kilns. When 

 the kilns are built in rows, two air ducts are placed in each side wall 

 and the partition walls between the furnace rooms of the individual 

 kilns are omitted. This is brought out in Figure 4. To give more 

 uniform results, the furnace is set in a square concrete or masonry 

 inclosure. This is a comparatively recent improvement in kiln con- 

 struction. It consists of a concrete inclosure 9 feet square and 4^ 

 feet high directly in the middle of the furnace room. This has three 

 openings, each 18 inches by 4 feet, on three sides of the inclosure, and 

 the fourth side has a portion 4 feet wide cut away to serve as a fire 

 door. The upper portion of this opening is covered with a sheet-iron 

 door. On top of this wall a hopperlike structure is built, the bottom 

 corresponding to the top of the concrete inclosure and the top meeting 

 the side walls of the kiln at a point 3 feet below the drying floor and 

 13 feet from the ground. The frame of this hopper is of 2 by 4 inch 

 scantling, covered on the inside with metal laths and three-eighths of 

 an inch of cement plaster. The sides of the hopper are made per- 

 fectly tight, so that no air can reach the drying floor without entering 

 the bottom of the hopper through the air ducts. This prevents un- 

 equal drying on the sides of the kiln as a result of wind, and at the 

 same time the hopper prevents loss of heat by radiation through the 

 side walls. Many operators believe that properly constructed hop- 

 pers reduce the fuel consumption by at least 15 to 20 per cent. The 

 details of construction are shown in Figure 1. 



The drying flo<or. — The drying floor carries considerable weight and 

 must be strong. The usual type of construction is to have two wood 

 or steel beams set into the side walls of the kiln and spaced evenly. 

 The joists are placed at right angles to these girders and are set back 



