20 METEOROLOGICAL OBSERVATIONS 



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 Ib. in 1903) ; 

 but the minimum result (3*30 Ib.) was obtained in 1890, 

 when the rainfall amounted to 24*78 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 Ib. 



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

 ammonia and nitrates does not represent the whole amount 

 supplied 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 Ib. 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 (T09 per million), and the 

 maximum (4*17 per million) in the January rain. The 

 amount falls and rises in the intermediate months with 

 considerable regularity, the only break occurring in the 

 March rain, which contains more chlorine than the rain 

 falling in February. The total chlorine is equivalent to 25 '3 Ib. 

 of common salt per acre per annum. Of this amount, 17*0 Ib. 



