28  DESCRIPTION  OF  PHARMACEUTICAL  APPARATUS. 
involved  in  the  manufacture  of  ointments  and  paints,  and  for  the 
several  processes  of  frictional  mixing,  with  which  the  druggists' 
apprentice  is,  unfortunately  for  himself,  too  familiar.  The  abra- 
ding or  triturating  action  is  performed  by  a  pestle  with  an  in- 
geniously arranged  differential  motion,  which  we  shall  describe 
with  the  help  of  three  illustrative  figures  : 
Fig.  3. 
Fig.  I.  Fig.  2. 
Figure  1  is  a  front  elevation  of  the  triturator,  showing  the 
pestle  and  actuating  gearing.  Figure  2  is  a  corresponding  side 
elevation  ;  and  figure  3  is  a  detail  for  the  gearing  of  the  differen- 
tial movement  of  the  pestle.  The  mortar,  A,  is  seated  in  the  base 
of  a  timber  frame,  B,  the  upper  part  of  which  carries  the  driving 
