328 
USE  OF  FUNNELS  IN  DISPLACEMENT. 
so  slowly  that  in  one  case  fermentation  took  place  and  the  whole 
became  worthless. 
It  will  be  recollected  that  according  to  the  directions  of  Prof. 
Grahame  all  substances  designed  for  displacement  are  to  be 
powdered  so  as  to  pass  through  a  sieve  of  40  or  60  meshes  to 
the  linear  inch,  according  to  the  permeability  of  the  material : 
then  moistened  to  such  extent  only  as  that,  the  pulverulent 
character  being  not  entirely  lost,  the  particles  shall,  when  rubbed 
between  the  hands,  move  freely  upon  each  other  ;  then  packed 
into  the  apparatus  more  or  less  firmly  in  proportion  as  the  mass 
possesses  this  mobility,  or  is  adhesive,  and  then  the  whole  of  the 
liquid  being  poured  on  to  the  top  it  is  allowed  to  proceed  to 
completion. 
This  process  was  so  novel  and  contrary  to  my  previous  ex- 
perience that  I  should  not  have  given  it  a  trial,  but  for  the  de- 
servedly high  reputation  of  its  author,  his  positive  assurances  of 
its  success,  and  the  evidences  he  had  long  ago  shown  me  of  the 
superiority  of  his  percolated  preparations.  One  point  in  his  ex- 
periments which  had  appeared  of  no  importance  to  him,  had 
attracted  my  attention  as  likely  to  increase  the  difficulties  of 
the  process,  and  I  had  accordingly  omitted  any  attention  to  it 
in  my  manipulations  ;  he  had  always  used  a  funnel  which  he  said 
was  not  objectionable,  as  generally  supposed,  and  had  the  ad- 
vantage of  being  always  at  hand,  cheap  and,  when  of  glass, 
allowed  an  opportunity  to  inspect  the  uniformity  of  the  packing 
and  the  gradual  progress  of  the  displacement.  I  had  always 
objected  to  the  use  of  the  common  funnel  for  any  of  the  more 
difficult  displacements,  and  had  stated  in  the  first  edition  of  my 
work  on  pharmacy,  that  in  treating  rhubarb,  senna,  squill,  &c, 
with  any  menstruum  containing  a  considerable  proportion  of 
water,  the  displacer  must  be  a  cylinder  with  a  broad  and  coarse 
diaphragm,  and  that  a  common  funnel  with  a  plug  of  cotton  in 
the  tube  was  quite  out  of  the  question. 
Now,  to  an  accidental  trial  of  the  common  funnel,  with  a  po- 
rous powder  dampened  and  tightly  packed,  as  directed  by 
Grahame,  I  owe  the  discovery  that  I  had  all  along  been  mis- 
taken, and  that  the  shape  of  the  apparatus  was  perhaps  the 
chief  though  the  unsuspected  cause  of  Grahame's  success  in  per- 
colation. 
