ILLINOIS DAIRYMEN'S ASSOCIATION. 39 



peal to the pride and self interest of the producer to assist in a scheme which 

 will meet out equal justice to all and produce good returus. There are but 

 few men who cannot be reached by these two forces. Those who cannot, 

 had better be set adrift, for they are so mean they will steal from the manu- 

 facturer or their neighbors, without a doubt. This much in general, about 

 good milk. 



The next important step of butter making is the separation of the cream 

 from the whole body of the milk. The principle underlying the varions pro. 

 cesses for accomplishing this is well set forth by J. D. Frederickson of New 

 York. He says : ''In new milk, the butter globules are suspended in the 

 milk-serum, or watery solution of the other constituents, in a mechanical 

 mixture — an emulsion, so-called. The specific gravity of the butter globules 

 being less than that of of the milk-serum, the former have a tendency to 

 rise to the surface of the latter, whenever new milk is left alone. With a 

 small part of the milk-serum, the butter globules farm a layer of cream oq the 

 top of the serum, leaving the latter more or less poor in fat, as skim-milk. 

 The active agency causing the separation of the cream from the skim-milk is 

 the difference in the respective specific gravities of the two parts. Any 

 means increasing that difference will further the separation. By intense 

 cooling of new milk, the serum, being the better conductor of heat, is cooled 

 quicker than the butter globules; and as, therefore the former is shrinking 

 more rapidly than the latter, the difference in specific gravity is increased, 

 causing the cream to rise more quickly." All devices for raising cream, of 

 whatever kind, were intended to take advantage of the conditions found in 

 cows milk as stated above, although the inventors, in most cases were igno- 

 rant of them. They knew that the cooling of the milk would raise the cream 

 but the philosophy of the process was until recently, a sealed book While 

 all the old inventions aimed to make the dilference between the specific grav- 

 ity of the cream and serum greater by the application of cold, or rather by 

 the extraction of heat ; now comes the separator and reaches the same end by 

 centrifugal force. The difference being that the latter is vastly more pow- 

 erful and will do good work where the cooling process will fail. Centrifugal 

 force is simply another means by which to iocrease the tendency of the two 

 parts of the milk to separate on account of the difference in specific gravity, 

 but this method is a thousand times more active than cooling or heating, or 

 any other design as yet proposed. When a particle of matter is swinging 

 around a central point, the force by which it presses outward from the center 

 of revolution depends upon the gravity, the speed, and the distance from the 

 center. In other words for lOOO revolutions a minute, the distance from the 

 center being one foot, the centrifugal force is 340 times the weight of the mat- 

 ter; the distance from the center being two feet it is 680 times the weight of 

 the matter, the distance from the center being three feet it is 1020 times the 

 weight of the matter. Now to show how this force is exerted upon cream and 

 skim milk, suppose the weight of a particle of fat in milk be 10 weight-units 

 and that of an equally large particle of milk-serum be 11 weight-units, then the 

 force by which the fat is naturally driven toward the surface will be 11—10=1, 

 while in the centrifugal machine, making 1000 revolutions a minute, with an 

 average radius of 1 foot, the force will be the difference between 340x10 and 



