Much trouble and annoyance have been experienced by both buttermakers and creamery patrons on account of the variation of different individual tests of milk for butter fat, and the variation of milk from the same herd at different times, the test going up and down, sometimes with no apparent cause. These variations have sometimes caused the patrons of a creamery to suspect that the buttermaker was engaged in manipulating the test in a discriminating way to further his own ends, while on the other hand the buttermaker may have had strong suspicions that the patron whose test varied greatly might be guilty of adding water or cream, or both, to his milk at one time, and at another taking cream from the milk and retaining it at home. All of the...