382  Agricultural  Chemistry. 
the  evidence  of  others  whose  writings  have  formed  this  Journal, 
not  to  obtrude  any  fancied  discoveries  of  my  own. 
In  taking  this  review  I shall  reverse  the  order  adopted  in  the 
former  survey,  and  say  first  a few  words  on  the  scientific  rather 
than  begin  with  the  practical  part  of  farming.  My  reason  for  the 
change  is  this: — The  proper  relation  of  science  to  agriculture  has 
frequently  been  mistaken.  It  has  been  supposed  that  science, 
especially  chemistry,  was  to  guide  and  direct  practical  farming  by 
conclusions  termed  on  chemical  grounds  beforehand,  and  this 
mistake  has  not  been  without  its  effects.  It  is  worth  while  then 
to  consider  the  true  relation  of  chemistry  towards  agriculture. 
Common  chemistry  teaches  the  action  of  substances  upon  each 
other,  as  of  an  acid  upon  an  alkali,  mixed  in  a vessel  together. 
Organic  chemistry  endeavours  to  show  the  action  of  substances 
upon  each  other  within  the  vessels  of  an  animated  frame,  whether 
plant  or  animal ; but  the  chemist  does  not  say,  because  a mineral 
acid  decomposes  an  organic  salt,  “ I advise  a gouty  patient  who 
has  chalk-stones  on  his  fingers  to  drink  oil  of  vitriol,  and  get  rid 
of  them.”  He  knows  that  the  powers  of  life  are  too  complicated 
for  him,  and  leaves  diseases  to  be  dealt  with  by  the  physician.  The 
physician,  a man  who  has  studied  the  art  of  medicine,  that  is,  the 
recorded"  experience  of  ages,  knows  practically  that  certain  drugs 
have  certain  effects,  and  he  administers  them.  Tut  a few  years  since, 
when  it  was  found  that  soluble  flint  is  contained  in  wheat-straw, 
silicate  of  soda,  a salt  of  flint,  was  advertised  and  sold  for  some 
time  to  farmers,  that  the  straw  of  their  crops  might  be  thus 
strengthened,  and  the  crops  might  not  be  laid  any  more — an  evil 
experienced  widely  however  this  year.  The  chemist  has  aided  the 
physician  in  a different  way.  The  physician  found  the  efficacy 
of  a certain  bark  in  fevers.  The  chemist  has  extracted  from  the 
woody  fibre  a white  powder  like  sugar,  which  contains  all  its 
medical  properties.  So  Baron  Liebig  has  taught  the  farmer,  who 
already  knew  that  bones  were  good  for  turnips,  how  to  treat  those 
bones  with  sulphuric  acid,  and  present  the  phosphorus  to  the 
young  plant  in  a more  digestible  form.  But  eight  years  ago  it 
was  supposed  that  we  must  supply  to  plants  in  manure  nearly  all 
the  mineral  ingredients  contained  in  their  ashes.  Thus  Baron 
Liebig — (I  mention  an  error  of  his,  because  his  high  reputation  will 
not  be  injured  thereby,  and  the  warning  may  be  useful  toothers) — 
that  eminent  philosopher,  I say,  prepared  and  sold  under  patent 
a manure  containing  the  mineral  ingredients  of  wheat  so  prepared 
as  to  be  slowly  soluble,  and  therefore  to  supply  what  the  wheat 
wanted  when  it  was  wanted.  Ammonia  was  omitted,  because 
ammonia,  it  was  thought,  would  be  supplied  by  the  air.  The 
scientific  manure  was  applied,  but  the  wheat  did  not  mend.  The 
mineral  theory  then  eagerly  adopted  was  contained  in  the  following 
