306 AGRICULTURE FOR COMMON SCHOOLS 



twenty-four hours, when nearly all of the fat will have risen 

 to the top. This method is quite effective and the amount of 

 fat left in the skim-milk is often not more than .2 of 1 per cent. 



3. A dilution separator is a can into which the milk is 

 poured and then diluted with water, usually one-half. The 

 can is made with a faucet so that the skim-milk can be re- 

 moved from the bottom. The can is kept in a cool place or 

 in cold water. When the milk is diluted the fat rises to the top 

 more quickly. There are several objections to the dilution 

 system : (a) The water used always has some germs in it. 

 However, they may not always be injurious, (b) The cream 

 obtained is not of the best quality, (c) The diluted skim-milk 

 is not so good to feed to pigs or calves, (d) The fat is not all 

 removed, as much as .7 of 1 per cent, or more may be left in 

 the skim-milk. All experiment stations condemn the dilution 

 separator. 



4. The centrifugal separator is a machine. The milk runs 

 into a bowl which is revolved several thousand times per 

 minute. The revolving has a tendency to throw the heaviest 

 particles to the outside of the bowl. Since the fat is not so 

 heavy as the other parts of the milk, it would, therefore, be 

 crowded toward the centre of the bowl. The cover of the 

 bowl is so constructed that the cream, or fat, can escape from 

 the centre of the cover, while the skim-milk escapes from 

 openings nearer the edge of the bowl. There are many dif- 

 ferent kinds of separators and each has a differently con- 

 structed bowl. Most bowls have inside parts intended to 

 spread the milk out in thin layers so that the centrifugal force 

 can act more completely. There are some bowls which have 

 no inside parts. They are known as hollow bowls. The sep- 

 arator does not separate the fat entirely by itself, but also 



