Page:Popular Science Monthly Volume 43.djvu/116

106 The Babcock milk-testing machine is now just as generally sold by dairy firms as is an improved churn or butter-worker.

One of the most wonderful of agricultural inventions is the centrifugal or milk separator. Briefly, this machine is designed to separate the cream from the milk as soon as drawn from the cow, thus dispensing with the old process of setting milk and waiting for the cream to rise by gravity. At the International Dairy Show at Hamburg, in 1877, an instrument was exhibited consisting of two wheels in a stand, one of which actuated the other by means of a belt. In the upper wheel four glass tubes containing milk were securely placed, and the lower wheel was then revolved, giving the upper upward of one thousand revolutions per minute. Whirling at this speed brought centrifugal force to bear on the milk in the tubes, and the cream, being lightest, collected at one end and the skim milk at the other.

In 1879 De Laval, a Swede, exhibited to the British public at Kilburn a centrifugal separator entirely unlike the preceding one, and this machine of De Laval, in principle and general plan, is the form now commonly used over Europe and America. Milk, warm from the cow, is conveyed into a hollow steel drum about ten inches in diameter, which is made to revolve six thousand to seven thousand times per minute within a slightly larger metal chamber. The skim milk, being heavier, is thrown to the outside, and passes off through a tube which rises from a point in the skim milk where the least amount of fat exists to the upper edge of the drum; while the lighter cream rises near the center of the drum and passes off through another hole, coming out of the separator on the opposite side from the skim milk. One or two thousand pounds of milk an hour may be creamed with this machine, when run by horse or steam power. Several other designs of centrifugals have more recently been invented, some of greater capacity than the De Laval, but at the present day the modern De Laval's is unsurpassed. For small dairies De Laval invented a hand separator, which is known as "the baby separator." With the No. 2 size one person can separate the cream from three hundred pounds of milk in an hour, the drum making six thousand revolutions per minute to forty-two turns of the crank.

The manufacture of this cream separator has been followed by the invention and introduction within the past two years of a combined cream separator and butter extractor, which makes it