27 



is 340 times the weight of the matter; r being 2 feet, it is 680 

 times; r being 3 feet, it is 1,020 times the weight, etc. Supposing 

 the weight of a particle of fat in the milk to be 10 weight-units, 

 and that of an equally large particle of milk serum to be II 

 weight-units, then the force by which the fat is naturally driven 

 towards the surface by gravity only will be n 10=1, while in 

 the centrifugal machine making 1,000 revolutions a minute, with 

 an average radius of I ft., the force will be 340x11 340x10= 

 340. Thus the tendency of separation is increased 340 times by 

 the centrifugal forces, and if the speed is 5,000 revolutions per 

 minute, the increase will be 8,500 times. This gives an idea of 

 the efficacy of centrifugal creaming as compared with any gravity 

 process, and also suggests the enormous strain to which the drum 

 of a separator is subjected. Supposing a stick to make a thousand 

 revolutions a minute around its center in the horizontal plane, 

 at each end carrying a pail with milk weighing 60 pounds, and 

 supposing the average radius to be 2 feet, then the force with 

 which each pail will pull the stick is 340x2x60=40,800 Ibs., or 

 about 20 tons." 



CONDENSED HISTORY OF THE CREAM SEPARATOR. 



Prof. Fuchs, of Carlsruhe, in 1859, suggested the testing 

 of milk by swinging it in test tubes. In 1864 Mr. A. Prandtl, 

 of Munich, experimented .with hanging cylindrical buckets with 

 milk on a revolving spindle. In 1870, Rev. H. T. Bond, of Massa- 

 chusetts, had two glass jars fixed on a spindle, revolving only 200 

 times per minute. In 1873 Mr. Jensen, of Denmark, had two 

 pails revolving 400 times a minute. In 1872 Prof. Moser showed 

 a model in Wien, and in 1874, Lefeldt, of Braunschweig, showed 

 the first large separator. It consisted of a drum provided with a 

 partial cover and four vertical partitions. It was encased in a 

 heavy mantle. 



The drum revolving 800 times a minute would keep the milk 

 (220 Ibs.) in a vertical position. It took 5 or 10 minutes to get up 

 full speed, 20 to 30 minutes to separate and '25 to 30 minutes to 

 come to a standstill again. When the milk had resumed its hori- 

 zontal position, the cream floated in a heavy layer on top. The 

 milk was removed with a siphon and the cream drawn through a 

 valve in the bottom of the drum, which was refilled and the 

 operation repeated. In 1878 the writer learned to operate this at 



