MATERIAL RESOURCES OF LIFE. 339 



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 posses- 

 sion; 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 poverty and of riches rest in the chemical elements. 



With the definition 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 a 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 jDlant. 

 How much carbon is taken from the organic mould of the soil and from 

 acid carbonates, through the roots, is perhaps not fully settled; but we are 

 well assured that the main and sure resource of the plant for this element 

 is the air. The supply, 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 view- 

 less air to every plant alike, the carbon-atoms are supplied for the frame- 

 work of every cell in plant and animal. A dwarfed shrub or rootless 

 lichen, clinging to the crevices of a naked rock on a frigid shore, 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-suj)ply in the air is not a reservoir diminishing, how- 

 ever slowly, from age to age; but, to be sure, it is a returning fountain, 

 replenished from the exhalations of animals and the decomposing remains 

 of all organized bodies. In Nature's economy, the same carbon-atoms are 

 used over and over again as material for organization. This perpetual re- 

 plenishment, a thrifty provision against future exhaustion, is one not pecu- 

 liar 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 cen- 

 tennial at j!Torthumberland, Pennsylvania, two years ago, placed it on 

 record very clearly that "air vitiated by animal respiration is a pabulum 

 to vegetable life." This was but the next year after Priestley's discovery 

 of oxygen itself; yet to this day there lingers in our common thought an 



