SEPARATION OF CREAM. 131 
In 1875 Prandtl exhibited at Frankfort-on-the-Main a con- 
tinuous .separator, which did not at the time attract much 
attention, due chiefly to the excessive amount of power needed 
to overcome the resistant force of the air. In 1876 a Danish 
engineer named Winstrup succeeded in improving the old 
bucket method. In 1877 Lefeldt and Lentch offered for sale 
four continuous separators with different capacities (from 110 
to 600 pounds of milk per hour). During that year also the 
first practical centrifugal creamery was established at. Kiel, 
Germany. In 1877 Houston and Thompson of Philadelphia 
filed a patent for the continuous method of separation of cream 
MSS fil 
Fic. 70.—First centrifugal separator. (From Dairy Messenger.) 
from milk. The patent was allowed in 1891. In March, 1877, 
Lefeldt and Lentch invented a separator similar in construction 
to the hollow bowl—a more recent type. This machine did not 
revolve at so rapid a rate as our modern machines do, nor 
did it have arrangements for continuous inflow and discharge. 
It was intermittent in its work, and it was necessary to stop 
at intervals to remove the cream and skimmed milk. 1879 
was the year which marked the greatest advancement toward 
the perfection of modern separators. The appearance of the 
Danish Weston, invented in Denmark, and the De Laval, in- 
vented in Sweden during that year, marked a great advance- 
