THE MATERIAL RESOURCES OF LIFE. 341 



in the sense of exchangeable value, in society ; even though needed as 

 they are in more constant supply than those of the other class. The 

 resources which are barely adequate are those which come to be objects 

 of personal possession ; they are the things of which mine and thine 

 are declared, and it is because of them that title-deeds are drawn and 

 prices-current established. The substrata of jjoverty and of riches 

 rest in the chemical elements. 



With the detinition of each class in mind, let us now consider the 

 supply of some of the more important of the elemental resources. 

 From the fourteen, let us take at least three elements of each class, 

 as representatives. For the redundant resources, we will take carbon, 

 oxygen, and hydrogen. Then, for the adequate resources, we will 

 examine nitrogen, phosphorus, and potassium. 



Carbon is the one element never left out of an organic compound. 

 Its atoms are not only constituents, they are corner-stones of all the 

 organic molecules. In the human body, thirteen parts in a hundred, 

 or forty per cent, of the solids, are carbon. Looking for its supply, we 

 see that it is obtained for the organic world by the plants, and from 

 the carbonic-acid gas of the air. It is taken from the air chiefly by 

 the leaf of the plant. How much carbon is taken from the organic 

 mould of the soil and from acid carbonates, through the roots, is pei*- 

 haps not fully settled ; but we are well assured that the main and sure 

 resource of the plant for this element is the air. The sifp2)li/, then, is 

 as abundant and impartial as the open air itself. The carbon-material 

 forms but a small part of the air, it is true, only about five parts in 

 10,000; nevertheless, it is enough, at least for the average rate of 

 vegetable nutrition. Carried around the globe in the viewless air to 

 every plant alike, the carbon-atoms are supplied for the framework of 

 every cell in plant and animal. A dwarfed shrub or rootless lichen, 

 clinofing to the crevices of a naked rock on a frigid shoi*e, has at hand 

 a good supply of the same resource that is furnished to a luxuriant 

 palm spreading from a tropic soil. 



And the carbon-supply in the air is not a reservoir diminishing, 

 however slowly, from age to age ; biit, to be sure, it is a returning 

 fountain, replenished from the exhalations of animals and the decom- 

 posing remains of all organized bodies. In Nature's economy, the 

 same carbon-atoms are used over and over again as material for or- 

 ganization. This perpetual replenishment, a thrifty provision against 

 future exhaustion, is one not peculiar to carbon, but it is a provision 

 made in good degree for every one of the elemental resources of life, 

 whether redundant or only adequate in its immediate supply. 



That plants feed upon the carbonic acid of the air is known to the 

 school-children, and has been known to men for a hundred and one years 

 at least. Priestley, whose discoveries were celebrated in the chemical 

 centennial at Northumberland, Pennsylvania, two years ago, placed it 

 on record very clearly that " air vitiated by animal respiration is a pab- 



