324  New  Determinations  of  Ammonia,  Chlorine,  and 
correct,  what  estimate  can  be  given  of  the  amount  of  combined 
nitrogen  annually  furnished  by  the  rain  at  Rothamsted  ? 
If  we  take  the  results  of  the  daily  determinations  during 
six  months,  June  to  December  1881,  as  representing  half  a 
year,  then  the  nitrogen  as  ammonia  supplied  in  the  rain  in 
the  course  of  one  year  will  amount  to  2-374  lbs.  per  acre.  If 
we  take  the  results  furnished  by  the  analyses  of  fresh  monthly 
mixtures  during  two  years,  the  annual  amount  becomes 
2 466  lbs.  per  acre.  If  the  analyses  of  old  monthly  mixtures 
are  included,  the  quantity  of  nitrogen  as  ammonia  becomes 
2-662  lbs.  per  acre  per  annum.  The  quantities  shown  by  these 
three  methods  of  estimation  agree  well  together,  but  the  first 
will  probably  most  nearly  represent  the  ready  formed  ammonia 
supplied  by  rain  ; we  have  learnt,  indeed,  that  in  the  case  of 
the  Rothamsted  rain-water,  collected  in  a leaden  gauge,  the 
quantity  of  ammonia  tends  to  increase  with  the  age  of  the 
wTater,  a part  of  the  organic  nitrogenous  matter  present  in 
the  rain  doubtless  undergoing  decomposition,  ammonia  being 
produced. 
The  two  series  of  determinations  of  nitric  acid  in  Rothamsted 
rain,  made  by  Way  and  by  Frankland,  have  been  described 
in  the  earlier  Report.  Way’s  results  of  two  years’  (1855-6) 
analyses  of  rain,  gave  a mean  of  0"12  of  nitrogen  as  nitric  acid 
per  million  of  water  ; equal  to  0-75  lb.  of  nitrogen  per  acre  for 
the  years  in  question.  Frankland,  using  a more  modern  method 
of  analysis,  found  a nearly  similar  proportion  of  nitric  acid  in 
rain-water.  The  numerical  mean  of  34  determinations  in  rain, 
excluding  dew,  gave  0T4  of  nitric  nitrogen,  while  the  average 
amount  in  28  rainfalls  of  which  the  quantity  was  known,  was 
0- 149  of  nitric  nitrogen  per  million  of  water.  If  wTe  reckon  the 
present  average  rainfall  at  Rothamsted  (about  29  inches)  on  the 
latter  estimate,  the  quantity  of  nitrogen  as  nitric  acid  annually 
supplied  in  the  rain  becomes  nearly  1-0  lb.  per  acre.  The  total 
nitrogen  as  ammonia  and  nitric  acid  is  thus  about  3'3  lbs.  per 
acre  per  annum. 
We  have  yet  to  take  account  of  the  nitrogenous  organic  matter 
present  in  rain-water.  The  mean  quantity  of  nitrogen  in 
organic  combination  found  by  Frankland  in  69  samples  of 
Rothamsted  rain  was  0T9  per  million  of  water,  while  the  average 
amount  in  the  mixed  rainfall  of  56  collections  of  known  quantity 
was  0"165  per  million.  Taking  the  last-named  estimate,  and 
with  an  assumed  rainfall  of  29  inches,  the  quantity  of  nitrogen 
as  organic  matter  annually  contributed  in  the  rain  becomes 
1- 08  lb.  per  acre.  In  the  case  of  Frankland’s  analyses,  however, 
the  samples  of  rain-water  were  of  some  age,  and  a part  of  the 
organic  nitrogen  had  doubtless  become  ammonia. 
