130 BUTTER-MAKING. 



as the separation can be done before the milk gets old, whilt 

 by the gravity method the time required for efficient separation 

 is so long that the cream deteriorates more or less before it is 

 removed from the milk. Third, by the centrifugal method the 

 thickness of the cream can be regulated to suit requirements, 

 while by the gravity method the thickest cream that can be 

 obtained is about 20%. Fourth, by the centrifugal method 

 many impurities and undesirable germs are removed, while in 

 the gravity method the exposure to open air more or less 

 impure is likely to contaminate the milk with taints, and also 

 allows the germs to fall into it. Fifth, by the centrifugal method 

 the skimmed milk is left in an unadulterated condition. The 

 milk can be skimmed soon after milking, or after it has been 

 delivered to the creamery, and thus be in the best possible 

 condition for feeding purposes. Sixth, the centrifugal method 

 permits of a more thorough separation of the fat. Butter-fat, 

 as a rule, is too expensive to feed, when good and much cheaper 

 substitutes can be had. 



History of Centrifugal Separators. — The first centrifugal 

 separator was a very simple one. It consisted of buckets 

 hanging on the ends of arms, or on the periphery of a rotating 

 horizontal flat wheel which swung on a central axis. The milk 

 was placed in the buckets and whirled for a time, and then 

 the machine (if we may call it such) was stopped, and the 

 cream removed in the same way as in the gravity system. 

 This method of separation, according to J. H. Monrad,* had 

 its origin in 1864. As early as 1859 Professor Fuchs of Carls- 

 ruhe, Germany, suggested testing the richness of milk by swing- 

 ing tubes holding the samples of milk. In 1864 Prandtl, a 

 brewer of Munich, separated milk by such a device. In 1870 

 Rev. F. H. Bond, of Northport, Massachusetts, worked out a 

 method of separation which consisted of two small glass jars 

 attached to a spindle making 200 re-\'olutions per minute. By 

 one hour's whirling the cream came to the top. 



* Dairy Messenger, Oct., 1892, p. 109. 



