596  PoMo  Starch  and  Other  Starches.      { "^"^  cec'/im 
POTATO  STARCH  AND  OTHER  STARCHES  OF 
COMMERCE. 
By  William  A.  S.  Johnson,  Ph.  G. 
From  an  Inaugural  Essay. 
The  manufacture  of  potato  starch  being  an  important  industry  on 
Prince  Edward  Island,  I  visited  one  of  the  largest  of  the  factories, 
situated  about  fifteen  miles  from  Charlottetown.  As  is  usually  the 
case,  it  is  built  on  the  banks  of  a  stream  where  a  constant  supply  of 
clean  water  is  always  at  hand.  The  establishment  is  capable  of  turn- 
ing out  about  eight  tons  of  starch  daily,  but  is  worked  only  for  a  few 
months  in  the  autumn  when  new  potatoes  can.be  procured. 
rhere  are  now  ten  factories  on  the  island  capable  of  making  about 
2500  tons  of  starch  during  the  season,  which  is  largely  shipped  to  Eng- 
land and  the  United  States,  where  it  is  principally  used  in  the  arts. 
When  desired  for  use  as  an  article  of  diet,  it  is  preferable  when  about 
a  year  old,  as  it  is  then  harder. 
The  potatoes,  after  being  weighed,  are  dumped  into  a  cellar  which  is 
connected  by  means  of  a  shoot  with  a  revolving  cylinder  having  a 
stream  of  water  running  through  it.  The  bottom  of  this  shoot, 
instead  of  being  solid,  consists  of  a  number  of  small  iron  rods  placed 
longitudinally,  and  about  an  inch  apart,  which  allows  the  dirt,  etc.,  to 
fall  through.  From  the  cylinder,  the  potatoes  fall  into  a  long  inclined 
trough,  full  of  water,  which  has  beaters  or  paddles  revolving  in  it. 
The  last  two  of  these  are  broad  and  flat,  and  after  the  potatoes  have 
gone  the  full  length  of  the  trough  and  have  been  thoroughly  washed, 
they  are  thrown  by  the  flat  paddles  into  a  box  having  a  cylinder  about 
six  feet  long,  and  twenty-two  inches  in  diameter,  covered  with  iron 
like  a  nutmeg  grater,  and  turning  at  the  rate  of  700  revolutions  a 
minute.  This  grates  the  potatoes,  making  them  into  a  pulp  which 
is  washed  by  a  stream  of  water  on  to  long  sieves  made  of  number  70 
brass  wire  which  are  kept  in  rapid  motion.  Over  these  is  placed  a 
long  box  with  a  bottom  of  zinc  having  three  longitudinal  lines  of  per- 
forations, through  which  steady  streams  of  water  pour  on  the  sieves 
washing  all  the  starch  through,  while  the  fibre,  etc.,  is  shaken  off  and 
washed  away.  The  starch  wat^r  is  carried  into  a  series  of  tanks  about 
10  X  12  feet,  and  6  feet  deep  where  it  is  allowed  to  settle,  which  takes 
from  seven  to  eight  hours.  The  water  is  then  drawn  off  and  the  tanks 
are  filled  again.    After  the  starch  has  all  settled  and  the  water  run  off 
