332  On  the  Power  of  Soils  to  absorb  Manure. 
combination  takes  place,  and  the  result  is  carbonate  of  lime  and 
sulphate  of  ammonia.  The  change  acts  beneficially  by  pro- 
ducing a more  fixed  salt,  which  has  no  great  tendency  to  escape 
into  the  air,  but  it  does  not  protect  from  loss  where  water  gains 
access,  because  the  sulphate  of  ammonia  is  a highly  soluble  salt. 
H ere,  however,  comes  the  great  peculiarity,  when  we  have  in 
addition  to  deal  with  the  soil.  The  sulphate  of  ammonia  gives 
up  its  acid  to  lime,  and  sulphate  of  lime  comes  through  in  the 
filtered  liquid.  It  would  be  premature  to  assert  here  that  this 
change  did  or  did  not  occur  through  the  agency  of  carbonate 
of  lime ; but  supposing  that  carbonate  of  lime  was  the  acting 
substance,  we  have  a distinct  reversal  of  the  ordinary  chemical 
laws : thus,  for  instance,  we  might  under  this  presumption  mix 
carbonate  of  ammonia  with  sulphate  of  lime,  the  result  being  an 
interchange  of  the  acids  and  bases ; the  mixture  then  being 
incorporated  with  a soil,  we  should  again  have  gypsum  and  car- 
bonate of  ammonia,  the  latter  being  combined  in  some  way  with 
the  soil.  Such  a reaction  would  be  quite  possible  supposing  the 
power  of  the  soil  to  arrest  and  combine  with  the  carbonate  of 
ammonia.  It  would  indicate,  however,  that  this  power  was  one 
of  great  activity,  since  it  was  sufficient  to  reverse  altogether  the 
ordinary  chemical  laws.  My  object  in  dwelling  upon  this  point 
is  to  show,  that  supposing  the  power  under  discussion  to  resemble 
that  of  charcoal  and  other  porous  substances  for  ammonia,  and, 
further,  granting  that  carbonate  of  ammonia,  as  possessing  in  part 
the  gaseous  character  of  the  free  alkali,  was  subject  to  the  same 
law,  then  it  would  be  quite  conceivable  that  the  different  salts  of 
ammonia  should  come  under  its  influence  by  virtue  of  the  trans- 
forming power  of  carbonate  of  lime  in  the  soil.  The  law  would 
then  simply  resolve  itself  into  one  of  a physical  character,  af- 
fecting the  ammonia  and  its  carbonate  directly,  and  the  other 
salts  by  indirect  action. 
Highly  interesting  and  important  in  both  a theoretical  and 
a practical  point  of  view  as  this  action  of  soils  upon  ammonia 
and  its  compounds  would  be  if  it  went  no  further,  it  by  no 
means  comprehends  the  whole  question,  and  we  shall  now  pro- 
ceed to  detail  experiments  which  render  it  necessary  to  modify 
if  not  altogether  to  abandon  the  notion  that  the  absorption  is  of 
the  nature  of  the  gaseous  condensation  exhibited  by  charcoal  and 
other  porous  bodies. 
Absorption  of  Potash. 
Experiment  43. — Caustic  potash.  Solution  of  caustic  potash  was  thrown 
upon  a 10-inch  filter  of  Mr.  Pusey’s  soil.  The  solution  employed  gave 
abundance  of  double  chloride  of  platinum  and  potassium  when  treated 
with  chloride  of  platinum  ; but  the  liquid,  after  percolation,  contained  no 
potash  in  any  form,  which  had  therefore  been  arrested  by  the  soil. 
