321 
On  the  Power  of  Soils  to  absorb  Manure. 
left  in  contact  for  24  hours,  and  then  a fresh  portion  of  the  former  was 
added  ; what  now  came  away  was  perfectly  free  from  ammonia,  and  tally 
half  an  ounce  was  collected  in  which  neither  ammonia  nor  its  salts  could  be 
detected. 
The  solutions  of  ammonia  in  these  first  two  experiments  were 
evidently  unnecessarily  strong,  and  it  required  close  attention  to 
observe  the  different  stages  of  the  absorptive  process.  A standard 
solution  to  be  employed  in  the  succeeding  experiments  was  there- 
fore made  by  diluting  1 oz.  of  strongest  ammonia  with  60  ounces 
of  water  ; this  solution  was  analyzed  approximative^,  and  found 
to  contain  about  0’3  per  cent,  of  real  ammonia.  Although  thus 
diluted  it  was  highly  pungent  to  the  nose. 
Experiment  3. — 5000  grains  of  the  same  soil  in  coarse  powder,  in  a tube 
24  inches  long;  the  column  of  soil  occupying  18  inches;  solution  of 
ammonia  ('3  per  cent.)  poured  upon  it.  The  solution  took  about  half  an 
hour  to  percolate,  and  about  4 ounces  came  through  before  ammonia  or 
its  salts  could  be  detected. 
At  this  stage  of  the  investigation  the  idea  suggested  itself,  that 
the  effect  observed  might  be  nothing  more  than  a mere  displace- 
ment. The  soil  employed  was  simply  dried  in  the  air,  and, 
although  pulverulent,  was  found  still  to  contain  20  per  cent,  of 
water.  It  might  reasonably  be  supposed  that  the  solutions 
in  filtering  downwards  would  displace  this  water,  which  would 
first  issue  from  the  bottom  of  the  tube,  and  would  of  course  contain 
no  portion  of  the  substance  with  which  the  experiment  was  made ; 
that  this  might  be  a fertile  source  of  error,  will  be  understood  by 
reference  to  the  last  experiment,  in  which  5000  grains  of  soil 
being  employed,  1000  grains  of  water,  or  more  than  2 ounces, 
would  have  to  be  displaced.  The  obvious  method  of  checking 
the  result  would  be  to  dry  the  soil  before  the  experiment ; but  in 
the  absence  of  any  knowledge  at  the  outset  of  the  nature  of  the 
supposed  action,  it  was  by  no  means  clear  that  if  such  a property 
did  really  exist,  it  might  not  be  destroyed  by  such  desiccation. 
The  following  experiment  was  therefore  designed  to  settle  this 
point. 
Experiment  4. — The  same  soil  was  passed  through  a sieve  of  40  holes 
and  retained  by  another  of  80  holes  to  the  inch,  so  as  to  ensure  a filter  of 
uniform  character.  Upon  a column  of  18  inches  of  the  above  a strong 
solution  of  common  salt  was  poured  : owing  to  the  equable  size  of  the 
particles  of  soil  the  solution  did  not  require  a lengthened  time  to  pass. 
The  first  drop,  which  came  through  in  about  five  minutes,  was  tested  by 
nitrate  of  silver,  and  gave  abundant  indications  of  chlorine. 
Experiment  5. — A similar  trial  with  exactly  the  same  result. 
The  rapidity  of  the  filtration,  and  the  strength  of  the  solution 
of  salt,  seemed  to  render  this  experiment  less  satisfactory  than  it 
otherwise  might  have  been.  The  next  is  not  open  to  the  same 
objection. 
VOL.  XI. 
Y 
