102 
THE  PROCESS  OF  PERCOLATION. 
lator  vessel,  6,  and  it  matters  not  whether  this  vessel  be  a  specie 
jar  or  a  mixing  tun. 
c  is  a  tube  standing  erect  in  the  centre  of  the  vessel,  and, 
upon  the  scale  of  the  drawing,  of  about  two  inches  diameter. 
This  tube,  if  of  metal,  has  about  one  inch  of  its  lower  extremity 
perforated  with  holes  ;  or  if  of  glass,  simply  broken  off  irregu- 
larly. Around  the  lower  end  of  this,  a  ball  of  clean  tow  or 
straw  is  wound  rather  loosely.  Over  the  tow  and  end  of  the 
tube,  the  centre  of  a  large  disk  of  blanket  is  passed,  and  tied 
firmly  around  the  tube  a  little  above  the  tow  or  straw..  The 
blanket  is  then  reflected  out  over  the  bottom  of  the  tub,  where 
it  forms  a  stratum  for  conducting  the  percolate,  as  shown  at  d. 
The  wetted  substance  to  be  percolated  is  then  filled  into  the  tub 
upon  this  blanket  and  around  the  tube,  and  packed  equally. 
The  menstruum  being  then  admitted  through  the  funnel  opening 
in  the  cover  at  g,  saturates  and  percolates  the  substance,  and 
passes  into  the  tube  or  well,  c,  rising  to  the  same  level  in  the 
well  that  it  is  in  the  tub  outside.  The  remainder  of  the  contri- 
vance consists  in  the  means  of  drawing  off  this  percolate  from 
the  well  by  a  syphon  that  shall  never  empty  itself,  and  of  regu- 
lating the  rate  at  which  this  is  accomplished.  The  syphon,  e, 
may  be  of  glass  or  metal,  or  what  is  much  better,  of  India- 
rubber  tubing.  It  should  pass  from  the  bottom  of  the  well  in- 
side the  tub  to  a  little  below  the  bottom  of  the  tub  outside,  and 
the  outer  end  should  be  furnished  with  a  small  piece  of  glass 
tube  bent  in  the  form  of  a  U.  Until  all  the  menstruum  has  been 
added,  the  free  extremity  of  this  U  should  be  kept  at  about  the 
level  of  the  substance  in  the  tub,  or  a  little  lower,  if  the  rate 
be  regulated  by  a  string  and  wedge.  But  when  all  the  men- 
struum has  been  added,  it  must  be  dropped  down  below  the  bot- 
tom of  the  tub.  By  the  U  shaped  end,  this  little  syphon  is  pre- 
vented from  emptying  itself,  so  long  as  there  is  liquid  in  the  well, 
no  matter  at  what  level  it  may  be  kept,  and  it  may  be  made  to 
keep  the  well  entirely  exhausted  of  percolate  if  desired,  or  to 
keep  it  at  any  given  level.  Indeed,  in  all  respects,  there  can 
hardly  be  a  more  manageable  or  convenient  arrangement  than 
this,  whether  for  operations  on  the  large  or  small  scale,  and  it 
may  be  recommended  as  the  cheapest  as  well  as  most  convenient 
percolater  known  to  the  writer. 
Louisville,  Ky.,  January,  1858. 
