Churnability  of  Cream. 
119 
expanded  to  its  full  extent,  so  offering  the 
greatest  resistance  to  the  plunger  passing 
through  the  cream.  When  the  plunger  is 
drawn  up  through  the  cream,  the  two 
halves  of  the  disc  which  formed  the  head, 
fall  together,  and  so  offer  the  least  possible 
resistance  to  the  upward  passage  of  the 
plunger  through  the  cream.  The  up  and 
down  movement  of  the  plunger  rod  actuates 
a lever  (see  Fig.  2)  to  which  a pencil  is 
attached.  This  pencil  is  applied  to  a 
moving  roll  of  paper,  and  records  on  it  the 
exact  length  of  each  stroke  made  by  the 
plunger  through  the  cream.  The  plunger 
falls  through  the  cream  simply  by  its  own 
weight,  but  is  lifted  through  it  by  means 
of  a special  mechanism  working  from  the 
rocking  lever  and  the  rocking  shaft  under- 
neath the  machine.  The  machinery  is  so 
adjusted  that  the  plunger  has  only  just 
time  to  fall  through  the  cream  when  it  is 
first  put  into  the  glass  jar  which  represents 
the  body  of  the  churn.  As  the  cream  gets 
thicker  the  plunger  does  not  fall  so  far 
through  it ; and  so  a shorter  line  is  drawn 
on  the  paper.  When  the  butter  “ comes,” 
it  is  possible  for  the  plunger  to  be  drawn 
up,  because  the  head  collapses,  and  so  offers 
little  resistance  ; but  the  downward  stroke 
of  the  plunger  is  arrested  owing  to  the 
resistance  offered  by  the  butter  particles  to 
the  open  disc.  It  was  expected  that  by 
placing  six  of  these  jars  in  a row — each 
containing  different  creams — and  churning 
them  simultaneously  the  churnability  of 
each  sample  of  cream  could  be  accurately 
compared.  In  some  experiments  6,000  to 
7,000  strokes  were  required  before  the 
butter  came  ; but,  though  a large  number 
of  experiments  were  made,  it  is  felt  that 
for  purposes  of  comparing  different  breeds 
further  research  work  is  necessary. 
One  curve  drawn  by  the  apparatus, 
however,  is  published  for  purposes  of  illus- 
tration. This  (Fig.  3)  shows  what  would 
appear  to  be  a normal  course  of  churning. 
In  1,500  strokes  it  will  be  seen  that  the 
Q 
B 
INDMHUBBER- 
Fig.  4. — Apparatus  for 
sampling  Milk. 
