120 SCIENCE AND PRACTICE OF DAIRYING. 



number, u the number of revolutions of a fatty globule in a minute, 

 and r the radius vector of a globule. From this formula, it is seen 

 that the centrifugal force acting on the fatty globule is in simple 

 proportion to the distance of the globule from the centre point 

 around which the revolutions are made, and increases in quadratic 

 proportion to the revolutionary speed. 



55. The Value of Centrifugal Force for the Creaming of Milk. 

 The natural force of gravity, which is universally and at all times 

 freely available, and which was formerly exclusively used in cream- 

 raising, acts with uniformity. Not merely does it require a certain 

 time in which to obtain the best possible results, but even under the 

 most favourable conditions it fails to obtain complete separation of 

 the cream from the milk. Much more perfect separation, and a 

 shortening of the time necessary for cream-raising, can only be effected 

 by the application of a force, which will impart to the fatty globules 

 an impetus far exceeding that given by gravity. This force is 

 centrifugal force. It is not to be had gratis, since its application 

 costs money; but it is at all times easily utilized for the purpose of 

 cream-raising, and can be applied in such a manner that its force 

 exceeds that of gravity to the extent of more than a thousand-fold. 

 It is only necessary to subject the milk, in suitable vessels, to a very 

 rapid rotatory motion. The idea of utilizing this force in dairying, 

 and thereby of curtailing the period for the separation of the 

 cream, does not date further back, it would seem, than the middle 

 of the century, when C. J. Fuchs carried out experiments in 

 Carlsruhe on cream separation by centrifugal force. About 1860 

 similar experiments were carried out by Albert Fesca, in Berlin, 

 and, in 1864, by Antonin Prandtl, in Munich. It was first demon- 

 strated to be practical in 1877 by the German civil engineer William 

 Lefeldt, in Schoningen, in Brunswick, who, after more than fifteen 

 years of arduous experimentation, succeeded in producing a milk- 

 separator, which, if imperfect, was nevertheless practical. Since 1877 

 the structure of milk-separators has been improved from year to year, 

 and at present there are quite a number of serviceable separators of 

 different structure known by different names. At present all 

 separators are so arranged that when at work they are fed with a 

 continuous stream of milk, and give out in return separated cream 

 and skim-milk. The utilization of these highly serviceable machines 

 has extended more and more, especially since efficient separators, 

 capable of being driven by the hand, have been devised, and they 



