334 PRODUCTIVE FARMING 



to bring it before the class and give a lesson in testing sam- 

 ples of milk and cream. Or perhaps it will be as well for the 

 class to take a trip to a near-by creamery and observe the 

 operation. If possible the school should own an outfit. 

 The students could then test samples of milk from the cows 

 of the neighborhood. 



Exercise. — Skim Milk and Buttermilk. — Samples of skim 

 milk from two or more separators should be tested to deter- 



FiG. 222. — The weight of each cow's milk is written on the record sheet. 



mine which one removes the cream the best. If butter- 

 milk is tested, this will tell how well the churning has removed 

 the butter. 



Principles of the Babcock Test. — The testing of milk by 

 this method is founded on the fact that very strong acid will 

 dissolve all the substances in the milk except the butter fat. 

 The particles of fat are thus set free from the rest. As the 

 fat is the lightest part of the milk, it will rise to the top. 

 This takes place in a few minutes if the bottles of milk are 

 placed in a whirling machine (centrifugal). In other words, 

 the heavier parts of the milk are thrown to the bottom. 



