124 SCIENCE AND PRACTICE OF DAIRYING. 



made in the drum, and which is only accessible from the wall of the 

 drum, and into which only skim-milk can come. The surface of the 

 skim-milk is thus brought as near as possible to the revolving axis. 

 In the case of such separators as those of Burmeister and Wain, the 

 cream and skim-milk are conducted from the surface, by means of 

 skimming-tubes, to the outside. 



59. The Regulation of the Proportional Weights of Cream and 

 Skim-milk in the Separation of Milk by Separators. In the drum of 

 every separator in use, the amount of cream and skim-milk which 

 flows out must be together equal to the amount of milk which flows 

 in. The proportion of the weight of cream to skim-milk is deter- 

 mined by the rapidity with which the milk enters the separator, 

 and in all separators, therefore, without exception, can be regulated 

 at will by this means when the separator is in motion. By this 

 method of regulation the amount of the cream obtained will be 

 altered, a thing which does not happen with an arranged equable 

 motion. For this reason, in almost all separators there are arrange- 

 ments whereby it is possible at will to regulate the quantity of 

 cream with a uniform inflow of milk. In the case of the separators 

 of Burmeister and Wain this is effected by sinking the skimming- 

 tube for skim-milk, either deeper or shallower, in the surface of the 

 liquid, a thing which can be very easily effected when the drum is 

 in motion. In the case of most other separators, the necessary 

 precautionary measures should be taken before creaming begins, 

 and while the drum is at rest. 



Where the place of outflow for the skim-milk is equidistant, and where 

 the conditions under which the milk flows out are otherwise the same, and 

 the outflow of the cream is riot in any way hampered, the more milk 

 that enters the drum in a definite time, the more cream will be given 

 out, the slower will the drum revolve, and the cooler will be the milk 

 which is to be creamed. The first case needs no further explanation. 

 With regard to the second, less skim -milk flows out in a definite time 

 under reduced pressure, and in consequence of this the surface of the milk- 

 ring is slightly moved towards the revolving axis, while in the third case 

 the friction towards the outflow exit is strongly increased, in virtue of 

 which the amount of skim-milk flowing out in a definite time is somewhat 

 diminished. 



60. The Size and Reliability of Separator-drums. The following 

 regulations are deduced from the equations given for calculating 

 the acceleration of separators in 54: 



