54 HARVESTING, STORING, AND MARKETING 



of apples in Eastern United States. Therefore, the index of 

 factory payrolls issued by the United States Department of 

 Commerce and the estimates of the Crop Reporting Board 

 should be watched. 



The volume of citrus fruit production seems to have much 

 less influence than has been claimed. 



It is evident that only the best grades of fruit represent 

 good storage risks under normal conditions. 



(6) Forms of Storage. The simplest form of storage is 

 that used by every farmer and by many a townsman, the 

 family cellar. The special common storage cellar or house 

 is a step further. Beyond this point are systems of cold stor- 

 age through the use of ice or by means of mechanical and 

 electrical refrigeration. 



Common storage answers a universal need. For its ef- 

 fectiveness it depends upon the control of the natural factors 

 of temperature, ventilation, and humidity. From the com- 

 mercial standpoint common storage is of importance in the 

 northern half of the United States where natural tempera- 

 tures range low enough to make it feasible. In much of the 

 Canadian apple belt and in some sections of the United States, 

 the weather is sharply cool, especially at night, before the 

 fruit is ready to pick. 



^^CoW storage, as it is termed, is provided through the use 

 of ice or ice and salt, or by a mechanical process which de- 

 pends on the compression followed by the expansion of gas or 

 vapor. As gas expands it takes up heat from its surround- 

 ings, lowering the temperature of a brine pumped through 

 pipes to the storage room. The material, having expanded 

 into its gaseous form, is condensed and returned to the com- 

 pressor to be used over again. Another method known as 

 the absorption system but not differing in final results is also 

 used. Ammonia gas is the material commonly employed. 



Very lov. temperatures are secured by mechanical refriger- 

 ation. Delicate and intricate devices control the tempera- 

 ture and humidity relations. A detailed discussion of cold 



