t 26 i 
multiplying the powers of a machine is to bring 
its operations within the reach of the force to be 
applied : More than this will only cause a loss of 
time in working it. A fourth 'point to be consult-f 
ed is, that no part of the power applied be wasted 
in producing useless effects. In the. common mode 
of churning, in lifting the dasher the resistance 
caused by the weight of the milk above is to be 
overcome, in order to produce the agitation requi¬ 
site for separating the butter from the milk, and in 
depressing the dasher it meets with equal- resist-: 
ance in forcing the milk from below. These are 
therefore effects that waste the power unnecessari¬ 
ly, for equal agitation can be produced without en¬ 
countering such resistances, and this is done by 
giving the dasher a horizontal instead of a perpen¬ 
dicular motion. It may be supposed that if there 
be any milk above and below a dasher moving 
horizontally there will be an unequal agitation« 
This however will be prevented by an incidental 
cause; for while the churning is performing, the 
milk will be carried by its centrifugal motion with 
considerable velocity against the sides of the 
churn, and their direction not being at right an¬ 
gles to the motion of the milk, but widening be¬ 
low, they must necessarily reflect it somewhat 
downwards. The consequence is that the milk will 
thus be continually, though slowly, forced down by 
the sides and made to rise through the middle of 
the ehiini; of course, all its contents will come 
successively under the strokes of the dasher* 
