J. H. Gilbert— P 



E I.— Combined Nitrogen i 



i connection with Vegetation. 





N.trogeo per acre, per annu m , Ib , 



1853. 



1855. 



1856. 



Mean. 





(not determined) 



M? 



0-'?3 



0-75 











663 



8-58 





LI1..1 S. 



merous determinations of the ammonia and nitric acid in 

 md the other aqueous deposits, have been made in various 

 of France and Germany, some in the vicinity of towns, 

 n the open country. Of the latter, which are the 

 purpose, it may be stated that those of Boussingault 

 'n Alsace, generally indicate a larger propor- 



Of the 



at Liebfra 

 tion of the n 



than our own ; but, upon the whole, the observations in the 

 idely separated localities mutually confirm one another. 

 " others, in other localities, some show about the 

 same amount of combined nitrogen so deposited as our own, 

 some, however, much more, and some much less, than ours; 

 but the determinations on the Continent generally show a 

 higher proportion of the total combined nitrogen to exist as 

 nitrates than those in this country. It may be added, that 

 numerous dt-t t in tio wo I the combined nitrogen in rain, dew, 

 etc., collected at Rothamsted, have much more recently been 

 made by Professor Frankkmd, and his re.-ult-. which are pub- 

 lished in the "Sixth Report of the Rivers Pollution Commis- 

 sion," are substantially confirmatory of the earlier determina- 

 tions, summarized in the foregoing Table, but upon the whole 

 tii. > indicate lower amounts. Lastly, M. Marie'-Davy deter- 

 mined the ammonia in the rain, etc, collected at the Meteoro- 

 logical Observatory at Montsouris, Paris, durino- the last six 

 months of 1875 ; and the amount of ammonia so doming down 

 even within the walls of Paris, represented only 5 -25 lbs. of 

 combined nitrogen per acre, or only 105 lbs. per acre, per 

 annum. M. Mane-Law did not make a complete series of 

 '■" A< "' 'oie nitric acid in the meteoric waters, but his 

 11,1 lul '' results a-r. ith th xp. rim t , tin , ,„ ,i ,, v 

 mg the amount of combined nitrogen to be comparatively small. 

 Thus, the determinations hitherto made of the amount of 

 combined nitrogen coming down in the measured aqueous 

 deposits from the atmosphere, do not justify us in assuming 

 that the quantity available from that source will exceed ei-dit 

 or ten lbs. per acre, per annum, in the open country, in Western 

 Europe. It should be observed, however, that the amount of 

 ammonia especially is very much greater in a <riven volume 



