46 THE LAND WE LIVE ON 



Hinrichs, all carbonic acid has disappeared. Boussingault 

 was the first to prove conclusively that the carbonic acid 

 in the air is used for the assimilation of carbon by plants, 

 and that other sources of carbonic acid, as from soil and 

 water, are of little consequence. 



A crop of wheat will remove one ton of carbon from 

 an acre of ground in four months, or as much as is contained 

 in a column of air 3 miles in height, and a crop of maize 

 removes in the same time about three times as much. 



Now the actual work done by the sun in the plant 

 tissue to produce this assimilation amounts to at least 

 3,000 horse power per day per acre, corresponding to the 

 work of 15,000 men. We can now understand what an 

 enormous amount of energy is wasted and lost for every 

 acre we leave even partially uncultivated. George Vilb, 

 in lectures delivered in 1883 at the Academy of Brussels, 

 puts this case very clearly. These lectures were translated 

 and edited by Sir William Crookes under the title " The 

 Perplexed Farmer,'^ and they should be read by every one 

 interested in agriculture. 



Another essential constituent of plant food is Nitrogen, 

 one of the most inert of elements, in this respect approach- 

 ing to the argon group. Although an inexhaustible supply 

 exists in the atmosphere, 4-5ths being pure nitrogen, the 

 higher plants cannot use it directly. It w^ould be almost 

 true to assert that the wdiole question of successful agri- 

 culture centres about the fixiation of nitrogen. This 

 essential of life is largely supplied to plants in the form of 

 that " villainous saltpetre " which, as gunpowder, we use 

 for the destruction of life. Nitrogen, indeed, performs 

 so important a role that one might almost christen agri- 

 culture " Azotism." Yet, I would remind you the very 

 word Azote, still used in France, was given to it for the 

 very reason that, per se, it is incapable of supporting life — 

 so involved are the processes of Dame Nature. 



Only some few of the micro-organisms are able to 

 assimilate atmospheric nitrogen directly ; all higher plants 

 must get their nitrogen in form of nitrates, and the prin- 

 cipal source of this combined nitrogen is the small amount 

 produced when organic substances are burned in air, and 

 by the direct union of oxygen and nitrogen in the air under 

 the influence of electric discharges. The extremely minute 



