325 
On  the  Power  of  Soils  to  absorb  Manure. 
and  composition  in  other  respects,  besides  the  destruction  of  the 
vegetable  compounds. 
Experiment  1G. — Mr.  Pusey’s  soil,  burnt  in  a covered  Hessian  crucible  in 
the  laboratory  furnace.  As  the  air  had  not  free  access,  the  quantity  of 
charcoal  distributed  through  the  soil  upon  the  cooling  of  the  crucible 
was  found  to  be  considerable.  The  tube  and  the  ammoniacal  solution 
were  the  same  as  in  Experiment  No.  1.  Owing  to  the  solidification  of 
the  particles  produced  by  the  burning,  the  liquid  sank  through  very 
rapidly,  and  coming  through  in  less  than  five  minutes,  did  not  appear  to 
be  at  all  diminished  in  strength. 
It  was  a second  time  passed  through,  with  no  better  result. 
Believing  that  this  failure  might  be  due  to  the  too  rapid  percolation  of 
the  liquid,  and  also  to  the  circumstance  that  the  solution  might  not  obtain 
access  to  the  interior  of  the  indurated  particles  of  soil,  the  following  ex- 
periment was  made : — 
Experiment  17- — The  same  burnt  soil  finely  powdered  and  rammed  down 
little  by  little  into  the  tube.  The  liquid  now  percolated  much  more 
slowly;  the  first  drops  which  passed  were  found  to  have  a very  slight,  but 
yet  perceptible,  odour  of  ammonia,  and  soon  afterwards  the  ammonia  came 
through  in  abundance. 
Experiment  18. — Mr.  Huxtable's  loam  burned  in  covered  crucible.  All 
organic  matter  was  destroyed,  but  the  charcoal  in  great  part  remained  ; 
18  inches  of  this  soil  was  used  as  the  filter  for  the  standard  weak  solution 
of  ammonia  (*3  per  cent.).  After  about  an  hour,  half  an  ounce  passed,  in 
which  no  ammonia  coidd  be  detected  ; caustic  potash,  however,  showed 
the  presence  of  some  ammoniacal  salt,  though  in  small  quantity;  subse- 
quently it  came  through  to  all  appearance  undiminished  in  quantity.  It 
was  evident  that  the  burnt  soil  had  the  power  of  retaining  ammonia, 
though  in  no  way  to  compare  with  that  of  the  unburnt. 
In  the  preceding  experiments  the  soils  used  were  cultivated 
soils,  and  contained  much  vegetable  matter,  yielding  a corre- 
sponding quantity  of  charcoal  when  burnt.  The  two  next  were 
made  with  a stiff  subsoil  clay  which  contained  comparatively  little 
organic  matter. 
Experiment  19.— A stiff  clay  from  Mr.  Huxtable,  burnt  in  a covered 
crucible  for  half  an  hour,  and  subsequently  powdered.  Part  was  black, 
but  the  greater  portion  was  red,  like  brickdust : the  burnt  clay  was  mixed 
with  its  own  weight  of  white  sand,  and  the  standard  solution  passed 
through  a column  16  inches  in  height.  About  half  an  ounce  of  liquid 
came  through  free  from  ammonia  or  its  salts,  but  the  power  of  the  clay 
was  sensibly  diminished  by  the  burning. 
Experiment  20. — The  same  clay  passed  through  a sieve  of  20  holes  to 
the  inch,  to  ensure  its  being  equally  acted  on  by  the  heat,  and  then  burnt ; 
very  little  charcoal  remained  in  the  red  brickdust  thus  produced.  The 
solution  of  ammonia  came  through  at  once,  and  appeared  undiminished  in 
strength. 
Experiment  21. — The  same  clay  sifted  as  before  and  burnt  very  strongly 
for  two  hours.  The  heat  ivas  sufficient  to  harden  the  clay  into  little 
lumps.  It  was  powdered  again  and  made  to  pass  through  the  same  20- 
hole  sieve.  The  column  of  the  filter  was  about  15  inches  in  depth.  The 
first  drops,  which  came  through  in  about  20  minutes,  smelt  strongly  of 
ammonia,  and,  so  tar  as  could  be  judged,  no  diminution  of  the  strength  of 
the  solution  had  taken  place. 
