Nitrogen  as  Nitric  Acid , in  the  Soils,  8fc.,  at  Rothamsted.  331 
TheTninimum  quantity  falls  in  July;  the  maximum  in  October 
and  November. 
5.  Determinations  of  sulphuric  acid  in  the  rain  of  two  years 
have  given  a mean  of  2*41  per  million  (reckoned  as  anhydride), 
or  18-5  lbs.  per  acre  per  annum.  The  sulphuric  acid  occurs  in 
nearly  equal  quantity  in  summer  and  winter. 
XVI. — The  Nitrogen  as  Nitric  Acid,  in  the  Soils  and  Subsoils 
of  some  of  the  Fields  at  Rothamsted.  By  Sir  J.  B.  Lawes, 
Bart.,  LL.D.,  F.R.S.,  J.  H.  Gilbert,  Ph.D.,  LL.D.,  F.R.S., 
and  R.  WAEINGTON. 
Contexts. 
PAGE 
Introduction  331 
Method  of  Soil-sampling,  and  of  Analysis  332 
History  of  the  Soils  examined 333 
The  Nitrogen  as  Nitrates  in  Soils  of  various  History  ..  337 
1.  Nitrates  in  Fallow  Land  338 
2.  Nitrates  in  Land  growing  Cereal  Crops  ..  ..  343 
3.  Nitrates  in  Land  growing  Leguminous  Crops  ..  361 
Summary  of  Results 365 
In  the  previous  Report  in  this  ‘ Journal,’  “ On  the  Amount  and 
Composition  of  the  Rain  and  Drainage- Waters  collected  at 
Rothamsted  ” (xvii.  [2]  241,  311  ; xviii.  1),  an  account  was 
given  of  the  quantities  of  nitrates  and  chlorides  found  in  the 
drainage-waters  from  the  uncropped  and  unmanured  soils 
forming  the  three  soil  drain-gauges  at  Rothamsted.  An  account 
was  also  given  of  the  amount  of  nitrates,  chlorides,  and  other 
constituents  found  in  the  drainage-waters  from  the  variously 
manured  plots  in  Broad  balk  Wheat-field.  Various  important 
conclusions  were  drawn  from  these  analyses  of  drainage-waters, 
and  especially  from  the  amount  of  nitrates  present,  which 
varied  greatly  according  to  the  cropping  and  manuring  of  the 
land.  We  now  propose  to  proceed  a step  further,  and  describe 
the  results  which  have  been  obtained  by  actual  determinations 
of  nitrates  in  soils  of  various  history. 
The  matter  at  our  disposal  embraces  miscellaneous  deter- 
minations of  nitrates  and  chlorides  in  various  soils  on  the 
Rothamsted  Farm,  both  fallow  and  cropped  ; and  also  a series 
of  determinations  of  nitrates  and  chlorides  in  the  soils  of  the 
variously  manured  plots  of  the  Experimental  Wheat  and  Barley 
fields.  The  examination  of  these  soils  has,  in  the  great 
majority  of  cases,  been  confined  to  the  depth  of  27  inches  from 
z 2 
