142 BUTTER-MAKING. 
inlet can be closed to such an extent as to cause nearly all the 
discharge to take place through the skim-milk tube. 
As a rule when the machine has been set so as to allow the 
milk to flow in at a certain rate, it will continue to admit prac- 
tically the same amount of milk all through the skimming 
period. Among the conditions which may alter the rate of 
inflow to some extent, are the amount of heat and the change 
of pressure, due to different amounts of milk in the receiving- 
vat. Temperature will slightly affect the rate of inflow. The 
higher the temperature, all other conditions being the same, 
the more milk will pass through the inlet. 
3. Speed.—All modern machines have a device by which their 
speed can be determined. Most speed indicators consist of a 
little wheel, which, when pushed up against the spindle of the 
separator while running, turns around and permits the calcu- 
lation of the speed of the separator. If the wheel on the speed- 
indicator turns 10 revolutions during ten seconds, the machine 
would turn 1000 times during the same time. During one 
minute the separator will run six times as many revolutions, 
or 6000, as ten seconds is one-sixth of a minute. Most speed- 
indicators are so adjusted as to turn one revolution for every 
100 revolutions of the machine. The higher the speed, the 
more thorough is the separation. Nearly all machines are 
balanced to do the best work at a certain definite speed, varying 
with different machines, and indicated in the directions for 
operating. It is essential that the machine should be brought 
up to speed gradually, and no milk be allowed to flow through 
it until after it has acquired its full speed. 
During the run, all machines are likely to vary more or less 
in speed, owing to different causes. Pulleys are likely to slip 
on the shaft, and belts are likely to become loose, and thus 
cause variations in the speed. The steam pressure is likely 
to get low, and cause all of the machinery in the creamery to 
run more slowly. This cause, however, is not a very common 
one where belt separators are used. If the engine has an auto- 
