20 METEOROLOGICAL OBSERVATIONS 



as parts per million and as lb. per acre. Other columns show 

 the relative proportions of the two combinations of nitrogen. 



Reference to the table will show that the average amomit 

 of nitrogen in the two forms is 3 "97 lb. per acre per annum, 

 and that most of the nitrogen is in the form of ammonia, 

 the nitric nitrogen representing only three-tenths of the whole. 

 The monthly variations show little regularity either in the 

 total nitrogen or in the relation of ammonia to nitrates. It is, 

 however, of interest to note that in the period April to 

 September, during which the rainfall is less than half the total 

 for the year, the rain contains more nitrogen than in the six 

 months October to March, and that the amount of nitric 

 nitrogen is nearly the same in both periods, the excess in the 

 warmer periods being mainly due to ammonia. 



When we compare the yearly amounts of nitrogen 

 in the rain, the variations are not found to be great, and 

 seem to have little if any relation to the rainfall. The highest 

 result corresponds with the highest rainfall (4-84 lb. in 

 1903); but the minimum result (3-30 lb.) was obtained 

 in 1890, when the rainfall amounted to 2478 inches. With 

 one of the lowest rainfalls of the period, however (20 '967 inches 

 in 1902), we get nearly the maximum amount of nitrogen, viz., 

 4-673 lb. 



It must be borne in mind that the nitrogen in the forms of 

 ammonia and nitrates does not represent the whole amount 

 suppHed to the soil. Frankland's results showed that the 

 rain contains besides the nitrogen in these forms a certain 

 amount of organic nitrogen, equal to about one-third of the 

 nitrogen as ammonia and nitrates. So that we may consider 

 that the average annual rainfall at Rothamsted contains 3 "97 

 plus 1 "3, or about 5 lb. of total nitrogen per acre. 



The amount of chlorine in the monthly samples of rain has 

 been determined at Rothamsted since 1877. The average 

 amount over the whole year is 2 '46 per million. The minimum 

 amount is in the July rain (1'09 per million), and the 

 maximum (417 per milHon) in the January rain. The 



