374 
On  the  Power  of  Soils  to  absorb  Manure. 
to  use  the  very  best  drills  in  the  application  of  artificial  manures 
in  his  experimental  field,  he  is  constantly  reminded  of  his  only 
partial  success  by  the  irregularity  of  the  crop.  It  is  obvious  that 
if  these  artificial  soluble  salts  remained  as  such  in  the  soil,  then 
distribution  by  rain  and  capillary  attraction  could  not  fail  of  ul- 
timately taking  place.  And  this  brings  me  to  notice  that  capil- 
lary action,  which  has  been  supposed  to  play  an  important  part  in 
the  changes  of  the  soil,  can  have  little  influence  except  on  those 
salts  which  are  really  in  a state  of  solubility  in  the  soils ; namely, 
the  salts  of  lime. 
The  methods  by  which  an  equal  distribution  of  manure  is  to 
be  effected,  must  be  left  with  the  farmer  and  the  agricultural 
machinist ; but  I may  observe,  that  much  of  the  wonderful  luxu- 
riance following  the  employment  of  liquid  manure,  may  fairly  be 
set  down  to  the  very  perfect  way  in  which  the  new  combinations 
in  the  soil  are  thereby  produced. 
The  absence  of  power  in  the  soil  to  unite  with  gypsum,  or 
in  any  way  to  retain  sulphuric  acid,  coupled  with  the  certainty 
that  sulphur  is  of  absolute  necessity  to  vegetation,  may  perhaps  in 
part  explain  the  advantage  of  applying  sulphate  of  lime  in  certain 
cases.  A soil  well  drained,  containing  naturally  little  gypsum, 
and  situated  in  a district  where  the  rainfall  is  considerable,  may 
be  supposed  to  stand  in  need  of  occasional  assistance  in  this  way. 
At  the  same  time  it  seems  as  if  nature  had  impressed  upon  gyp- 
sum a comparative  insolubility  in  some  measure  to  compensate 
for  the  impossibility  of  its  being  retained  in  the  soil  by  the  specific 
action  which  occurs  in  regard  to  other  compounds. 
The  newly  discovered  property  of  soils  explains  and  confirms 
the  variations  in  manuring  operations  which  are  made  to  suit  the 
nature  of  the  soil.  Clay  has  been  shown  to  be  the  active  sub- 
stance in  retaining  manure,  and  sandy  and  gravelly  soils  not  pos- 
sessing a sufficiency  of  clay  will  be  expected  to  be  less  retentive 
of  manure.  Such  is  the  fact,  and  soils  of  this  description  are 
said  not  to  “ hold  manure .”  On  such  soils  manure  must  be  ap- 
plied more  frequently  and  in  smaller  quantities  than  in  stiffer 
soils,  where,  owing  to  the  retentive  power  of  the  clay,  the  manure 
for  several  crops  may  be  safely  deposited. 
If  these  inferences  be  correct,  the  only  way  of  permanently 
improving  a sandy  soil  is  to  clay  it,  and  it  is  notorious  that  the 
light  sands  of  some  parts  of  Norfolk  are  only  made  to  bear  crops 
by  copious  dressings  of  clay.  It,  may  be  observed  in  passing,  that 
where  a dressing  of  clay  is  required  it  very  often  happens  that  the 
substance  at  hand  is  a marl,  of  which  more  than  half  is  carbonate 
of  lime,  which  (that  is,  the  carbonate  of  lime)  cannot  be  sup- 
posed to  be  a substitute  for  clay,  inasmuch  as,  although  it  is 
capable  of  improving  the  mechanical  texture  of  a sand  or  a gravel. 
