COOLING AND AERATION 47 
common, practice. The best of natural ice contains dirt 
and bacteria. Even ice made by mechanical means from 
distilled water often contains considerable quantities of 
impurities. Ice also is an adulterant just as much as 
water. In case of cream cooled with ice the body is un- 
satisfactory, even if the cream contains the required 
amount of fat. 
Cooling Without Special Coolers. When no special 
coolers are at hand milk and cream should be cooled 
in small cans by placing them in a tank or an oil barrel 
cut in two. Cold water is pumped into the tank or barrel 
in such a way that the cold water enters near the bot- 
tom of the tank, thus forcing out the warm surface 
water. 
Water should be pumped into the tank at frequent 
intervals until the milk or cream has nearly reached the 
temperature of the water. The time of cooling is ma- 
terially shortened by frequent stirring, which is a very 
essential part in cooling milk and cream in cans. 
Where milk is placed in large cans and stirred little, 
farmers lose in having the test lowered by hard par- 
ticles of cream forming at the top. Where milk is 
properly cooled, hard flakes of cream or churned cream 
will not be found on top of the milk. 
