130 BUTTER-MAKING. 
as the separation can be done before the milk gets old, while 
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 arule, 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 revolutions per minute. By 
one hour’s whirling the cream came to the top. 
* Dairy Messenger, Oct., 1892, p. 109. 
