THE VARIOUS TYPES OF FRUIT STOR.\GE 251 



coils. To cool the rooms, broken ice and coarse salt are put 

 into the vats and the ice in melting takes up the heat from the 

 primary coils, thus cooling the brine in them. This makes the 

 chloride brine heavier and it flows, by gravity, down through 

 the connecting pipe into the secondary coils. Here it takes up 

 the heat of the room and thereby becomes lighter again, and so 

 the flow is kept up. The temperature of the refrigerated rooms 

 is controlled principally by varying the amount of salt used 

 with the ice, but there are valves on the pipes by which the 

 flow may be stopped altogether when desired or shut down as 

 much as may be wished. The great advantages of the system 

 are: The cheapness with which it can be run, requiring no 

 high-priced labor whatever; the fact that one or more of the 

 rooms may be run without the others, thus reducing the cost 

 proportionately; the fact that there is no intricate machinery' 

 to get out of order, and repairs at their worst are made by a 

 plain plumber, and, most important of all, the fact that it works 

 well in practice. 



3. There is the frost-proof type of fruit storage. This de- 

 pends on the temperature of the outside air for cooling the 

 rooms. It is not as efficient as either of the others, but neither 

 does it cost as much, either to build or to operate. The old- 

 fashioned ^bam or house cellar is the crudest form of frost- 

 proof storage. The building shown in Figure 121 represents the 

 highest type. Where storage is required principally for winter 

 varieties of apples and where the autumn temperatures are 

 relatively low, the frost-proof house is likely to prove very 

 satisfactory. Where the more perishable fruits are grown it is 

 by no means so useful. Such a building or room is operated 

 by opening it up when the outside air is cooler than that of the 

 room and closing it again when the outside temperature rises. 

 With a little attention, and leaving it open during the cold 

 nights of early autumn, tlie temperature may be forced do\^^l 

 fairly low quite early in the season. 



Construction. — It may be worth while to give next the type 

 of construction used in the two buildings here described. 



