282 THE CIRCULATION OF NITROGEN [PART III 



Not all the products of nitrogenous decomposition which enter 

 the subsoil water or rivers reach the sea. On the land there are 

 plants, and microscopic organisms feeding like plants, and these 

 utilise some of the carbon dioxide, and nitrites and nitrates, as 

 food-stuffs. So also with regard to the rivers and lakes into which 

 land drainage enters. A certain fraction of the waste substances 

 produced upon the land is thus almost immediately again made 

 use of by terrestrial and fresh-water organisms, but a considerable 

 quantity does also reach the sea. 



How great is this quantity ? Obviously we can only estimate 

 its mass in an approximate degree. But we know what is about 

 the volume of water conveyed annually to the sea by the great 

 rivers of the earth ; and we know, in some cases, what is the 

 approximate quantity of nitrogen compounds contained in the 

 unit volume of the water of some rivers ; and therefore we can 

 calculate the approximate mass of nitrogen which drains from the 

 land into the sea. The Rhine discharges annually some 65,336 

 millions of cubic metres of water into the North Sea, and one litre 

 of this water contains, on the average, from 2 to 3 milligrammes 

 of nitrogen in the form of dissolved compounds^. Taking the 

 lower estimate we find that the Rhine alone carries 130 millions of 

 kilogrammes of nitrogen annually into the North Sea. If we take 

 the volume of all the other rivers entering this area as double that 

 of the Rhine we find that every year about 390 millions of 

 kilogrammes, or 383,000 tons of nitrogen are added to the North 

 Sea. Probably the volume of water carried down to the sea 

 from all the rivers of the world is not less than about 300 times 

 that of the Rhine. If we take it as such we find that every year 

 some 39 billions of grammes of nitrogen, or about 38 millions of 

 tons, are added to the oceans of the earth. 



This dissolved material entering the sea is at once dispersed 

 by the action of tides, winds and currents. The water near the 

 land ought to contain a greater proportion of these products of 

 land drainage than is found in truly oceanic areas. Nevertheless 

 it is difficult to demonstrate by actual analysis that this is really 



1 See Brandt, " Stoffwechsel im Meeres," Wiss. Meeresuntersuch. Kiel Komm. 

 Bd. IV. p. 230, 1899. The estimate is founded on Boussingault's and Hoppe-Seyler's 

 analyses. Brandt gives the references to the latter work. 



