The Herd and the Dairy 



267 



In large dairies a machine called a " clarifier " is used The 

 to free milk from impurities. In the clarifier milk is clari f wr 

 whirled so rapidly that foreign particles which are 

 heavier than milk are driven to the outer edge of the 

 machine, where they are drawn off. The force that 

 drives the heavier particles out of the milk is the same 

 force that throws the mud off the rim of a buggy wheel. 

 It is called " centrifugal force. If the milk were 

 allowed to stand long enough, the dirt particles would 

 be separated by being drawn to the bottom by the 

 force of gravity. But in the clarifier, centrifugal force 

 separates them much more rapidly than gravity could. 

 Milk treated in a clarifier is not easily digested and 

 therefore should not be used to feed small children. 



As we already know, milk from some cows is nearly 

 twice as rich as that from others ; and since the greater 

 part of the milk produced throughout the country is 

 used for butter making, it is very necessary to be able 

 to determine accurately the percentage of butter fat 



v '!'! 1 ! 1 ! 1 



Y, 1 ' 1 ' 1 " 



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U. S. D. A. 



FIG. 213. The open top permits all the dirt from above to fall into the bucket 

 at the left. The closed top keeps most of the dirt out of the other bucket. 



