158 
ON  NITROGEN  IN  MANURES  AND  SOIL. 
surface  equal  to  that  of  one  of  the  flower-pots  used  in  the  above 
experiments,  the  sand  took  0-0013  grams,  of  nitrogen  from  the 
air,  of  which  a  part  was  certainly  ammonia. 
The  object  of  the  researches  of  which  a  summary  is  given  in 
the  second  paper  was,  to  determine  the  quantity  of  nitrates  con- 
tained, at  a  given  moment,  in  one  hectare  of  cultivated  ground, 
one  of  meadow,  one  of  the  forest-soil,  and  in  one  metre  of  river 
or  spring  water.  The  quantity  in  the  soil  was  of  course  found 
to  vary  extremely  with  the  extremes  of  wet  or  dry  weather. 
Garden  soil,  highly  manured  every  autumn,  contained  on  the  9th 
of  August,  1856,  after  fourteen  dry  and  warm  days  316-5  grams 
of  nitre  in  a  cubic  metre  of  soil.  On  the  29th  of  the  month,  after 
twenty  rainy  days,  the  same  quantity  of  the  same  soil  contained 
only  13  grams  of  nitre.  The  greater  part  had  been  dissolved 
out  of  the  superficial  soil. 
Some  specimens  of  forest-soil,  in  a  state  of  nature,  furnished 
no  indication  of  nitrates :  others  gave  0-7  and  3-27  grams  of 
nitre  to  the  cubic  metre. 
The  soil  of  meadows  and  pastures  afforded  from  1  to  11  grams 
of  nitre  to  the  cubic  metre.  Nineteen  specimens  of  good  culti- 
vated land  gave,  four  of  them  none;  others  from  0-8  to  1-33  ; 
the  richer  ones  from  10-4  to  14-4,  and  one  fallow,  of  exceptional 
richness,  as  much  as  108  grams,  of  nitre  to  the  cubic  metre.  To 
the  latter  much  calcareous  matter  had  been  added. 
The  soil  of  a  conservatory,  from  which  the  nitrates  would  not 
be  washed  away  by  rains,  contained  89,  to  161,  and  some  rather 
deep  soil  185  grams,  of  nitre  in  the  cubic  metre. 
The  sources  of  the  nitre  are  not  difficult  to  understand  when 
we  reflect  that  a  manured  soil,  especially  a  calcareous  one,  is 
just  in  the  condition  of  an  artificial  nitre-bed.  The  ultimate  re- 
sult of  the  decomposition  of  ordinary  manure  is  a  residuum  of 
alkaline  and  earthy  salts,  phosphates,  and  nitrates,  the  latter, 
with  the  ammonia  furnishing  the  assimilable  nitrogen,  all-essential 
to  productive  vegetation.  In  incorporating  with  the  soil  unde- 
composed  manure,  instead  of  the  ultimate  results  of  the  decom- 
position, less  loss  is  suffered  from  prolonged  rains  washing  out 
the  formed  nitrates. 
The  soluble  matters  washed  out  of  the  soil  are  to  be  sought  in 
the  water.    River  and  spring  waters  therefore  act  as  manure  by 
