138 POPULAR SCIENCE MONTHLY. 



elements. Like Coleridge's Mariner, floating on the sea, surrounded 

 by the sea, and yet perishing for lack of water, so plants growing on 

 the bottom of the aerial ocean, with four fifths of its bulk consisting of 

 nitrogen, and that to a depth of 200 miles or more, would yet starve for 

 lack of nitrogen if there were not means in nature's workshop to com- 

 bine that very inert gas. Now, soils of average fertility contain rather 

 more than .1 per cent of nitrogen; in other words, the soil taken to a 

 depth of one foot contains 3,500 pounds of nitrogen to the acre. The 

 quantity is not constant, because of the various factors that lead either 

 to the increase or decrease of that treasure hoard which it had taken ages 

 to accumulate. In the processes of decay and fermentation, due to the 

 activity of molds and bacteria, much of the combined nitrogen is set 

 free and is returned to the atmosphere ; in all processes of burning and 

 explosion great quantities of nitrogen are again liberated. This latter 

 fact led Bunge to say that every shot fired kills whether it hits anything 

 or not, for it takes away that much life-giving substance from living 

 things. Then again, as the insoluble proteid molecules are broken down 

 and changed into simple salts, the nitrogen that thus becomes soluble, if 

 not taken up by the crop, is leached out of the soil, and ultimately finds 

 its way to the ocean. Enormous quantities of nitrates are thus car- 

 ried by the streams to the sea, there to feed its denizens, to return, per- 

 haps, in very slight measure to the land, though changed into other 

 forms. Thus the great swarms of coarse fish caught for fertilizer 

 purposes return in their bodies the nitrogen that had once traveled to 

 the sea; thus, also, the still extensive nitrate beds of arid South 

 America are a fractional return of what the sea had taken to itself. 

 That the dissolved nitrates poured into the sea year after year by streams 

 great and small do not remain there as such is clearly evidenced by the 

 analysis of sea-water which shows but traces of nitrates. And so it 

 appears that the soluble nitrogen salt, greedily taken up by plants in the 

 field, is also quickly consumed in the sea. Of course, the nitrate de- 

 posits of South America were not deposited from the ocean as such, 

 but resulted from the decay of great masses of seaweed. 



Then there are opposite tendencies. There are agencies which lead 

 to the increase of the nitrogen stock in the soil. It was Cavendish who 

 first showed that when electric sparks are passed through air confined 

 over a solution of caustic potash, small quantities of oxidized nitrogen 

 are formed. In a similar manner, the electric discharges in the atmos- 

 phere cause the formation of small quantities of combined nitrogen, and 

 Berthelot had shown that silent electric discharges also cause the 

 combination of gaseous nitrogen. Similarly it has been claimed that 

 in the burning of gas, coal, wax, etc., slight amounts of nitrogen become 

 combined. All these factors, and others not mentioned, are, however, of 



