ON  PERCOLATION  OR  DISPLACEMENT. 
323 
the  last  portion  of  the  pint  will  be  weaker  than  any  of  the 
others,  yet  when  all  the  proceeds  of  the  immediate  displacement 
are  mixed,  the  average  will  be  stronger  than  either  of  the 
others. 
In  conclusion,  I  will  offer  the  following  experiments  : 
1.  An  ounce  of  gentian  root  was  powdered  and  passed 
through  a  sieve  60  meshes  to  the  inch,  moistened  with  two  fluid 
drachms  of  water  so  as  to  be  yet  pulverulent.  It  was  put  in  a 
funnel,  the  neck  of  which  was  previously  stopped  with  moistened 
cotton,  slightly  pressed  and  covered  with  filtering  paper  and  the 
height  in  the  funnel  marked.  Water  was  now  poured  on  :  the 
powder  gradually  absorbed  its  bulk,  and  a  dark  brown  liquid 
collected  in  the  vessel  below.  The  densest  liquid  amounted  to 
3j  fluid  ounces,  but  more  than  eight  fluid  ounces  were  required 
to  exhaust  it.  The  first  liquid,  by  standing  a  few  hours,  gelatin- 
ized, from  the  large  amount  of  pectin  it  contained.  The  surface 
of  the  powder,  when  exhausted,  had  risen  half  an  inch  in  the 
funnel. 
2.  Two  ounces  of  Alexandria  senna,  of  similar  fineness  to 
the  gentian,  was  moistened  with  half  a  fluid  ounce  of  water,  and 
arranged  in  a  funnel  as  above.  Water  was  poured  on  and  was 
slowly  absorbed,  having  required  8  hours  to  become  saturated  ; 
a  dark,  nearly  black,  syrupy  liquid  gradually  collected  below, 
requiring  14  hours  to  four  fluid  ounces.  This  liquid  was  very 
highly  charged  with  the  properties  of  the  senna  and  very 
odorous.  The  powder  occupied  twice  its  original  bulk,  and  was 
gelatinous. 
3.  Two  ounces  of  senna  moistened  and  put  in  a  lamp  glass 
cylinder,  refused  the  passage  of  the  liquid  after  twenty-four 
hours,  owing  to  its  consistence. 
4.  Two  ounces  of  rhubarb  of  similar  fineness  was  moistened 
with  half  an  ounce  of  water,  (a  difficult  operation,  owing  to 
the  tendency  of  the  powder  to  form  a  paste  by  contact  with 
water,  and  thus  oppose  its  general  distribution  among  the  par- 
ticles,) and  treated  precisely  as  the  senna.  The  absorption 
took  place  with  great  slowness,  about  14  hours  elapsing  before 
the  liquid  commenced  to  pass,  and  20  hours  longer  were  requir- 
ed to  fill  an  8  oz.  vial.  Of  the  infusion,  about  one-half  was  satu- 
rated, and  above  this  the  liquid  was  less  dense,  but  quite  strongly 
