Action of the Atmosphere upon neidy-deepened Soil. 445 



Takinpf the ammonia that occurs in rain-water at the mean 

 found by Lavves and Gilbert, viz., about 1 grain in 1,000,000 of 

 rain-water, we should have brought down upon tlie plains of 

 Britain a yearly amount per imperial acre of 5544 lbs. avoir- 

 dupois of ammonia ; and supposing further that the nitric acid 

 brought down in the rain here bears the same ratio to the am- 

 monia as has been found by Barral at Paris (viz., as 16'25 to 

 3'49), we should have annually furnislied to the land by rain — 



. lbs. avoirdupois. lbs. avoirdupois. 



Ammonia .. .. .5'544 = nitrogen 4*565 

 Xitricacid .. .. 25-814 = ditto .. 6-693 



Total nitrogen in rain per acre .. 11-258 



Mr. Lawcs gives as the mean result for the monthlv amount of 

 ammonia in rain, at Rothamsted, per acre, half a pound, which 

 would be just (3 lbs. of ammonia in the year, being rather more 

 than the above statement, arising doubtless from the quantity of 

 rain at Rothamsted being, during his experiments, greater than 

 what I have taken the average fall to be. 



The quantity of rain that fell at Paris during Barral's experi- 

 ments seems to have been a good deal less than usual ; he gives 

 the average monthly amount of ammonia per acre at O'Sl lbs., 

 which would be 9"72 in the year. On an average of thirty years 

 it has been found that the mean annual fall of rain at Paris is 

 2G-6 inches. Supposing then that the proportions of ammonia 

 and nitric acid were to be the same for this quantity as Barral 

 found them to be during the five months of his observations, the 

 result per imperial acre in rain at Paris would be — 



lbs. lbs. 



Ammonia 21-061 = nitrogen 17-344 



Nitric acid .. .. 07-785 = ditto .. 25-352 



Total annual nitrogen in tlic rain .. 42-696 



As, however, it i.o generally noticed, that after some continuance 

 of rain the proportion of ammonia gets less, it is not perhaps 

 probable that quite so much would be conveyed in a year to the 

 ground. 



The annual fall of rain in Alsace, where Boussingault experi- 

 mented, may be taken as the same as at Paris. He found, during 

 observations of six months, March to Autjust inclusive, 0744 

 in 1,000,000 of rain ; taking the nitric acid in the same ratio as 

 at Paris, wc get in the rain per acre : — • 



lbs. lbs. 



Ammonia .. 4-477 = nitrogen 3-687 



Nitric acid .. .. 20-846 = ditto .. 5-405 



Total nit rocrcn I cr acre 9-092 



VOL. xvir. 2 ii 



