19 



IS 



It will be seen that, according to these results, an average of 6'84 

 pounds was contributed per acre per annum in the rain in the form 

 of ammonia and nitric acid. More recently, however. Dr. Frankland 

 has determined the amount of ammonia and nitric acid in numerous 

 samples of rain and snow water, dew, hoar-frost, &c., collected at 

 Rothamsted from April, 18G0, to ^lay, 1870, inclusive : and the average 

 amount of ammonia per million of water found by him is considerably 

 lower than the earlier determinations show. More recently .;till the 

 ammonia has been determined in the Rothamsted laboratory, in the 

 rain of each day separately (if any), for a period of six months, July- 

 December, 1881 ; also in the proportionally mixed rain for each 

 month, for a period o" thirteen months, June, 1881, to June, 1882. 

 The average proportion of ammonia in these most recent determina- 

 tions accords with the results of Dr. Frankland, and points to a 

 smaller amount of total combined nitrogen supplied per acre in the 

 average annual rainfall at Rothamsted than that recorded in the 

 table ; probably, indeed, to not more than four or five pounds of total 

 combined nitrogen per acre per annum. 



Dr. R. Angus Smith, in his work entitled " Air and Rain, the 

 Beginnings of a Chemical Climatology," 1872, gives the results of 

 numerous analyses of rain-water collected both in country and 

 town districts in the United Kingdom. The amounts of ammonia 

 and nitric acid in the rain vary exceedingly, according to 1 xlity ; 

 b\it the amounts in the rain of country places accord generally with 

 those found in the Rothamsted rainfall. 



The following table summarises the results of numerous determi- 

 nations made at various stations on the continent of Europe, in each 

 case extending over a whole year : — 



B 2 



