EVAPORATION OF FRUIT. 413 



which are manufactured by the American Manufacturing Com- 

 pany, of Waynesboro, Pa. It differs from the preceding in 

 having an inclined trunk. The advantages claimed for it by the 

 manufacturers are that separate currents of pure, dry air, auto- 

 matically created, pass underneath and diagonally through the 

 trays and then off over them, carrying the moisture out of the 

 evaporator without coming into contact with the contents of the 

 trays previously entered. The greatest heat is concentrated upon 

 each tray or group when first entered, these in turn being moved 

 forward into a lower temperature by those entered in sequence, 

 hence no steaming or cooking becomes possible. The evaporator 

 shown in the illustration is 9 \ feet long and 28 inches wide ; it 

 has 22 trays of galvanized iron cloth, and a capacity of 10 to 12 

 bushels of apples per day. It consumes about 80 pounds of coal 

 or its equivalent in wood or coke. The furnace supplies strong 

 currents of dry, hot air, which pass through the two chambers of 

 the evaporator-trunk and carry off the moisture or vapor dis- 

 charged from the fruit over and above the line of trays in each 

 chamber. jSTo steaming, cooking, or retrograde or diffusive 

 features attend the operation. The trays in groups of two at a 

 time are entered in front in the upper (hotter) chamber and 

 moved forward by insertion of the next group, and finished in 

 the lower chamber and at a lower temperature. Thus the process 

 is continuous, and each tray receives the same treatment and con- 

 ditions, viz., greatest heat when first inserted, and finishing at a 

 gradually lowering temperature and safety from scorching. The 

 evaporators are manufactured in several sizes ranging in price 

 from $25 to $450, and for extensive commercial plants with 

 sundry modifications and mechanism for coffee, tea, etc., of great 

 capacity costing $1000 and upwards. 



The manner of operating the Alden apparatus is as follows : 

 The maintenance of a uniform temperature in the tower being 

 essential, the thermometer should indicate 194 to 212 F. ; ber- 

 ries and stone fruit are to be kept somewhat cooler. The intro- 

 duction of too much cold air into the air-furnace must be avoided. 

 As a rule an aperture two feet square suffices. 



The upward motion of the trays must be effected at regular in- 

 tervals. How long these intervals are to be cannot be definitely 



