320  New  Determinations  of  Ammonia,  Chlorine,  and 
bably  be  nitrified.  We  must  thus  in  the  first  place  consider 
what  evidence  we  have  as  to  the  permanence  of  ammonia  in  the 
rain-water  samples. 
From  the  daily  analyses  of  rain-water  already  given,  the 
composition  of  the  water  for  each  month,  July  to  December 
1881,  has  been  calculated,  correction  being  made  for  the  few 
rainfalls  left  unanalysed.  The  calculated  composition  of  the 
monthly  mixtures  is  compared  below  with  their  actual  com- 
positions when  the  mixture  was  completed  ; and  further,  with 
the  results  of  an  analysis  of  these  mixtures  made  in  December 
1882. 
Month  (1881). 
Nitrogen  as  Ammonia,  per  million  of  Rain. 
Calculated 
from  daily 
Determinations 
(corrected). 
Determined 
in  Mixture  at 
end  of  Month. 
Ee-analysis, 
Dec.  18o2. 
^ July  
0-399 
0-618 
0-638 
August  
0 183 
0 178 
0 172 
September 
0-309 
0-350 
0-288 
October  
0-309 
0-214 
0-255 
November 
0-239 
0-237 
0-226 
December 
0-231 
0-196 
0-175 
Numerical  Mean . . 
0-279 
0-299 
0-292 
On  looking  at  these  figures  it  appears  that  the  ammonia  in 
the  rain-water  possesses  considerable  permanence ; in  one  or 
two  cases  only  is  there  any  distinct  diminution  of  ammonia 
by  keeping,  while  in  the  case  of  the  July  water  a considerable 
rise  has  taken  place.  Further  re-analyses  of  old  samples  of  rain- 
water, which  we  need  not  give  in  detail,  show  that  a considerable 
diminution  of  ammonia  by  keeping  is  rare,  and  the  increase  of 
ammonia  more  common.  In  fifteen  monthly  mixtures  of  rain- 
water the  mean  alteration  in  composition  during  1 to  1^  year 
was,  in  fact,  from  0’457  to  0'478  of  nitrogen  as  ammonia  per 
million  of  water.  The  rise  in  ammonia,  which  is  observed  in 
some  of  these  cases,  is  probably  due  to  the  decomposition  of 
the  nitrogenous  organic  matter  contained  in  the  rain.  That 
the  ammonia  in  rain  should  be  apparently  so  little  liable  to 
nitrification  will  probably  excite  surprise ; it  must  be  recol- 
lected, however,  that  the  rain-water  in  question  contains  a very 
distinct  amount  of  lead  in  solution,  derived  from  the  gauge 
in  which  it  is  collected,  and  this  is  very  probably  fatal  to 
the  life  of  the  nitrifying  organism. 
In  Table  III.  the  means  calculated  from  the  determinations  in 
