The Nature of the Agitation 213 
length of time will give butter of the best quality. 
The lower the temperature at which the butter is 
churned, other things being equal, the more com- 
pletely will the butter be removed from the butter- 
milk, the longer will be the time required for churn- 
ing, and the less casein will be found in the butter. 
The nature of the agitation.—It is generally be- 
lieved that the best results follow from agitating 
the cream in such a way that the particles of fat 
are subject to more or less concussion, though it 
is not at all necessary that this concussion should 
take place. Mere gentle stirring of the cream, if 
continued long enough, will bring butter, and agi- 
tating the. cream by passing bubbles of air through 
it will also cause it to churn. % Many ‘churns have 
been devised which bring about the churning by 
agitating the cream with floats or paddles, and in 
the old-fashioned dash churn there was a minimum 
amount of concussion, the motion being largely that 
of stirring. Where the agitation is brought about 
by the use of paddles or stirring instruments, the 
texture of the butter is usually injured, because of 
the effect of the stirring motion upon the grain of 
the first particles of butter formed. The best churns, 
then, are entirely hollow vessels, barrel or box, 
which bring about agitation of the cream through 
concussion of the particles upon the sides of the 
rotating churn. The churning depends, also, upon 
the rate of. agitation; the faster the motion to 
which the particles of cream are subjected, the 
quicker will be the churning. In this respect the 
