178 Milk and Its Products 
been the chief factor in revolutionizing methods of 
butter-making. By its greater efficiency it has pre- 
vented otherwise unavoidable losses, and by its greater 
economy of labor it has rendered possible the devel- 
opment of a profitable industry in many localities 
where it would have been otherwise impossible. 
In separating cream in a centrifugal. machine, the 
centrifugal force generated in a rapidly revolving 
bowl is made to take the place of the force of grav- 
ity acting upon the milk at rest in a vessel. The 
amount of force generated is so much greater than 
the force of gravity that the separation of the par- 
ticles of fat is much more rapid and much more 
complete. The force, however, acts in a horizontal 
instead of a vertical direction. In 1877, a patent was 
granted to Le Feldt & Lentsch for a machine to sepa- 
rate milk by centrifugal force. This first centrifugal 
separator consisted merely of a series of buckets hung 
upon arms swinging from a central axis. When the 
machine was at rest the buckets assumed a vertical 
position, but in motion they were thrown out horizon- 
tally from the arms. The milk was placed in these 
buckets, the machine set in motion until the cream 
was separated from the skimmed milk, and when the 
machine was allowed to come to a stand-still the 
buckets assumed a vertical position, and the cream 
‘was removed from the top in the same way that it 
was skimmed from any other vessel. From this was 
evolved a machine consisting of a revolving bowl 
or drum in which the separation takes place, with 
arrangements for removing the skimmed milk and 
