68 COOLING 
milk cans, and have an overflow at this level. 
They should also have a deep outlet, so that all 
the water can be drawn out and the tank cleansed. 
Galvanized iron tanks can be bought cheaply ready 
made for this purpose. One large cake of ice 
a day is usually sufficient for the average dairyman. 
In such tanks as this the bacteria in the night's 
milk will be no more numerous than the bacteria 
in morning’s milk when delivered next morning. 
TANKS OF RUNNING WATER 
Some farm wells contain water as cold as 42°. 
Spring-water is likely to be warmer than well- 
