100 MODERN FRUIT MARKETING 
precaution that is necessary to consider is the water- 
proofing of the outside walls to prevent moisture from 
getting into the filler or the papers used on the inside. 
All of the heavy work, stone and cement, is coated with 
pitch or some substance to make it impervious to 
moisture. Each set of material inside is also coated. 
In addition, from the inside many precautions must be 
taken to prevent the moisture from collecting on the 
walls in sufficient quantity to wet the insulating ma- 
terials. 
Mechanism of Cold Storage.—There are two well- 
recognized systems for cooling down storage houses: 
(1) Ice refrigeration, and (2) Mechanical refrigeration. 
The cheaper and most common used material is ice, espe- 
cially in the Northern states and the smaller houses. The 
larger storage houses in the big cities or those of the 
Southern states use mechanical refrigeration. It is difficult 
to give any estimate of comparative cost because of the 
wide variation in conditions, labor, cost of material, ete. 
As a general rule, for small or local cold storage houses 
ice is considered the cheaper, especially in the Northern 
states where ice can be manufactured in the winter at 
a low cost. Farther south it would be necessary to make 
the ice artificially and the cost would be much greater 
than for mechanical refrigeration. 
In the larger cities of the East where public storages 
are common, the mechanical system is used almost ex- 
clusively and by most operators is conceded to be the 
cheapest and the most economical to operate. Storage 
houses, up to 5,000-barrel capacity, will probably be 
cheaper to cool by ice than by mechanical means, and the 
smaller plants operated by cooperative organizations are 
