FRUIT STORAGE 103 
down and then by passing through the storage room take 
up the heat given off by the fruit. In such an arrange- 
ment, it is necessary to have two independent coils of 
pipes. The one that comes in contact with the ice and 
in which the cooling down is done is known as the 
primary coil, and the one that circulates through the 
storage room as the secondary coil. 
The principle of this circulation is just the reverse of 
the hot water system for heating buildings. The primary 
coil is the one highest up and as the brine in the cireu- 
latory system is cooled down it becomes heavier and 
settles to the bottom. As it circulates through the stor- 
age room it absorbs the heat from the room and expand- 
ing becomes lighter and rises again, until it reaches the 
primary coil. In this way a constant flow of the liquid 
through the pipes keeps the air in the storage room at 
the desired temperature without the bad effect of the 
moisture-ladened air coming into direct contact with 
the fruit itself. In most of these types of storage houses, 
the ice is harvested during the winter and stored in an 
annex to the regular plant. Then from this supply the 
ice is crushed as needed, elevated to the tank enclosing 
the primary coils, and fed in as desired. 
If the natural melting of the ice does not keep the 
temperature sufficiently low, salt is added to hasten the 
melting, the theory of the whole operation being that 
the ice in melting takes up the heat by absorption from 
the primary coil, thus cooling down the brine inside. 
The addition of the salt to the crushed ice only increases 
the rapidity of the melting; hence, increasing the absorb- 
ing power of beat from the surrounding atmosphere. 
Therefore, the more rapidly the ice melts the more rap- 
