HISTORICAL 87 



succeeded in separating cream in two glass jars at- 

 tached to a spindle making 200 revolutions a minute. 

 A Danish veterinarian in 1873, suspended two 

 pails on a stick revolving horizontally 400 revolu- 

 tions a minute, and secured the separation of cream. 

 The next step in the evolution of the separator was 



the vertical drum or cyl- 

 inder into which milk was 

 put and after revolving 

 till separation was secured 

 " valves in the periphery 

 of the drum were opened 

 and the skim milk allowed 

 to escape while in motion, 



FIRST CENTRIFUGAL SEPARATOR 



then closed and the drum 



stopped and the cream removed and a new supply 

 of milk put in." This was in 1876. In another ma- 

 chine of this type holding 220 pounds of milk, it 

 took ten minutes to attain a speed of 800 to 

 900 revolutions, and 24 to 33 minutes to come to a 

 stop, when the skim milk was siphoned from under 

 the cream, then the cream drawn through a valve 

 in the bottom of the drum. 



The third stage in the development soon followed. 

 In 1877 and ^78 appeared machines into which the 

 milk was fed continuously and the skim milk and 

 cream was taken out similarly. 



In 1879 m Denmark the Danish Weston and in 

 Sweden the De Laval Separators were developed 

 and marked the first great advance in the perfection 

 of a commercially successful machine. 



In 1890 De Laval discovered that certain internal 



