FRUIT STORAGE 99 
of the superstructure and to carry the enormous loads 
of the fruit or material stored. Then inside of these 
structures are placed the other insulating materials to 
protect the fruit from fluctuation in temperatures. In 
some instances dead air spaces are used next to the out- 
side construction, but in most cases they are filled with 
sawdust or some other loose substance. Then the use 
of several layers of matched lumber interspaced with 
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Y 
4 
Fig. 86.—APPLYING INSULATIONS 
building paper, air spaces or sheet cork gives a poor 
conducting power for the heat from the outside. 
The dead air spaces are at the present time being used 
less than in former years. While their insulating value 
is beyond question, yet it has been proved by experiment 
that it is almost impossible to make the dead air spaces 
tight enougr to prevent leakage or the circulation of 
air. And where leakage occurs, or moisture obtains en- 
trance, they rapidly lose in insulating value. Another 
