WATER AND ICE SUPPLY 277 



mechanical refrigeration, ice is indispensible in furnish- 

 ing the best quality of milk and cream. A low enough 

 temperature cannot be secured with water alone, neither 

 can the cooling be accomplished as quickly as is desirable 

 for best results. Furthermore, a satisfactory cold storage 

 cannot be had without the use of ice. 



Cooling Power of Ice. A great deal of cooling can 

 be done with a comparatively small amount of ice. This 

 is due to the latent or "hidden" cold in ice. Thus to 

 convert one pound of ice at 32 F. into water at the same 

 temperature requires 142 units of heat, or, in other words, 

 enough cold is given out to reduce the temperature of 

 142 pounds of water one degree Fahr. 



Construction of Ice House. To keep ice satisfactorily 

 three things are necessary, ( i ) good drainage at the bot- 

 tom, (2) good insulation, and (3) abundant ventilation 

 at the top. 



Good drainage and insulation at the bottom can be se- 

 sured by laying an eight-inch foundation of stones and 

 gravel and on top of this six inches of cinders, the whole 

 being underlaid with drain tile. One foot of sawdust 

 should be packed upon the cinders and the ice laid directly 

 upon the sawdust. 



Satisfactory walls are secured by using matched boards 

 on the outside of the studs and common rough boards 

 on the inside, leaving the space between the studs empty. 

 The ice should be separated from the walls by one foot of 

 sawdust. 



Where no solid foundation walls are provided, earth 

 must be banked around the ice house to prevent the en- 

 trance of air along the base. 



The space between the sawdust covering on top of the 

 ice and the roof should be left clear. Openings in the 



