323 
On  the  Power  of  Soils  to  absorb  Manure. 
filtration.  The  same  ammoniacal  liquid  was  employed,  and,  with  the; 
aid  of  a syringe,  4 ounces  were  passed  through  by  a lew  strokes  of  the 
piston  in  twice  as  many  seconds,  containing  no  ammonia  either  free  or  in 
combination. 
These  three  last-described  experiments  are  interesting,  as  indi- 
cating the  rapidity  with  which  the  absorption  of  ammonia  by  the 
soil  takes  place — a circumstance  which  leads  us  to  liken  the 
action  to  chemical  combinations  of  the  most  powerful  kinds,  such 
as  those  of  mineral  acids  for  alkalis  or  alkaline  earths.  It  also 
appears  that  in  conducting  experiments  on  this  subject  there  is 
no  occasion  for  any  j>rolonged  action  of  the  soil  upon  the  solution, 
provided  that  the  perfect  contact  of  the  two  is  attained.  Tihe  prac- 
tical bearings  of  this  point  are  very  important,  but  will  be  dis- 
cussed at  a future  opportunity. 
Although  it  did  not  seem  probable  that  this  particular  soil 
should  possess  so  singular  a property,  whilst  others  should  be 
found  destitute  of  it,  it  was  thought  advisable  to  operate  upon 
other  specimens.  The  following  experiment  was  made  with  the 
thin  soil  of  the  Dorsetshire  Downs  obtained  from  the  Rev.  Mr. 
Huxtable.  It  is  singular  that  this  soil,  which  is  only  a few  inches 
above  the  chalk,  does  not  give  a perceptible  effervescence  with 
acids. 
Experiment  12. — The  column  of  soil  in  this  experiment  was  18  inches, 
weighing  2390  grains.  The  solution  of  ammonia  of  the  same  strength  as 
before  ('3  per  cent.).  The  liquid  began  to  come  through  in  about  half  an 
hour,  and  when  more  than  3 ounces  had  passed  no  evidence  of  ammonia 
or  of  its  salts  was  obtained  in  it.  The  experiment  was  not  carried  further. 
H ere  then  we  have  a second  loamy  soil  which  possesses  the 
power  of  arresting  ammonia.  The  next  experiment  is  with  a 
yellow  clay,  which  forms  the  subsoil  of  Mr.  Huxtable’s  lower 
farm ; the  clay  was  not  examined  minutely,  but  it  was  ascer- 
tained that  although  containing  little  carbonate  of  lime,  it  was 
considerably  impregnated  with  gypsum.* 
Experiment  13. — Mr.  Huxtable’s  clay  powdered  and  passed  through 
20  hole  sieve,  and,  in  order  to  make  it  permeable,  mixed  with  its  own 
weight  of  well-washed  white  sand.  The  mixture  occupied  18  inches  in 
the  tube,  and  upon  it  solution  of  ammonia  of  the  usual  strength  was  poured. 
The  first  portions  came  through  in  about  two  hours,  and  several  ounces 
passed  the  tube,  but  no  ammonia  was  found  in  the  filtered  liquid. 
These  experiments  upon  three  different  soils  were  considered 
conclusive  as  to  the  existence  of  the  property  more  or  less  in  all 
* The  ear  is  familiar  with  the  name  of  gypsum  as  a “fixer”  of  ammonia,  and 
Irom  the  fact  of  this  soil  containing  it  some  readers  might  suppose  that  the  result  is 
due  to  its  presence.  Gypsum,  however,  only  “fixes”  ammonia  by  converting  its 
volatile  carbonate  into  the  sulphate  of  ammonia,  which,  although  not  liable  to  loss  by 
evaporation,  is  equally  soluble  as  the  carbonate,  and  would  pass  through  the  soil  were 
it  not  for  the  power  under  investigation. 
Y 2 
