330  New  Determinations  of  Ammonia , Sfc.,  at  Rothamsted. 
on  the  side  of  excess  in  summer  time,  owing  to  evaporation 
taking  place  in  the  collecting-bottle.  A part  of  the  sulphuric 
acid  in  the  Rothamsted  rain  will  be  due  to  coal-smoke,  and  a 
still  smaller  portion  derived  from  sea-spray.  The  considerable 
amount  of  sulphuric  acid  found  in  the  summer  rain  points,  how- 
ever, to  a further  source,  most  active  during  high  temperatures. 
This  indication  is  quite  in  accordance  with  the  opinion  held  by 
Dr.  Angus  Smith,  that  the  sulphuric  acid  in  rain  is  largely 
derived  from  the  products  of  the  decay  of  animal  and  vege- 
table matter,  which  is  of  course  most  active  in  the  warmer 
months. 
Before  leaving  the  subject,  we  may  notice  that  the  proportion 
of  chlorine  to  sulphuric  acid  in  sea-water  is  stated  at  about 
100  : 12  ; while  the  proportion  in  the  winter  rain  at  Rothamsted 
has  been  100  : 78,  and  in  the  summer  rain  100  : 194. 
Summary  of  Results. 
1.  152  analyses  of  rain,  snow,  dew,  and  hoar-frost,  repre- 
senting the  daily  collections  from  June  22,  1881,  to  January  5, 
1882,  gave  an  average  of  0"248  of  nitrogen  as  ammonia  per  mil- 
lion of  water;  the  extremes  observed  were  5-491  and  0-043. 
The  variations  are  dependent  on  the  richness  of  the  atmosphere 
in  ammonia,  and  on  the  quantity  of  the  rainfall,  the  smaller 
deposits  containing  the  most  ammonia. 
2.  Analyses  during  two  years  of  fresh  monthly  mixtures  of 
rain  gave  an  average  of  0"316  of  nitrogen  as  ammonia  per  mil- 
lion. Analyses  of  fifty  monthly  mixtures,  a considerable  number 
of  them  old,  gave  a mean  of  0'340.  The  rain  collected  in  the 
leaden  gauge  at  Rothamsted  generally  tends  to  increase  in 
ammonia  by  keeping.  The  rainfall  of  summer  is  generally 
richer  in  ammonia  than  that  of  winter. 
3.  The  nitrogen  as  ammonia  annually  supplied  by  rain  per 
acre,  reckoned  from  the  daily  determinations  of  six  months,  is 
2-374  lbs.  ; from  the  analyses  during  two  years  of  fresh  monthly 
mixtures,  2'466  lbs.  ; from  the  analyses  of  fifty  monthly  mix- 
tures, many  of  them  old,  2’662  lbs.  The  nitrogen  as  nitric 
acid  is  apparently,  from  Frankland’s  and  Way’s  results,  about 
TO  lb.  per  acre,  and  the  nitrogen,  as  organic  matter,  a similar 
quantity.  The  total  combined  nitrogen  in  the  annual  rainfall  at 
Rothamsted  would  thus  be  about  4-5  lbs.  per  acre. 
4.  Six  years’  determinations  of  chlorine  in  monthly  mixtures 
of  rain  give  an  average  of  T99  per  million  of  water,  or  14-92  lbs. 
per  acre,  equal  to  24-59  lbs.  of  pure  common  salt.  Two-thirds 
of  the  chlorides  fall  in  the  six  winter  months,  October  to  March. 
