_Energy._--Human exertion produces wealth, as we have seen, whenever it anticipates and provides for future wants by securing at hand the things to be used. So far as this anticipation includes control of forces or qualities in nature, these natural agencies contribute to wealth of individuals or communities. So voluntary human exertion is combined with involuntary forces of outside nature to give wealth. No amount of gold in Alaska is wealth until some human ability has appropriated it to human uses; but the mere fact of locating a claim for mining purposes gives the prospector advantage over any other man because of his foresight. So every activity of nature may become a factor in wealth by human ingenuity in making it useful.
_Natural forces._--Such natural agencies for producing wealth are seen in the simple properties of material bodies, such as the metals or woods or grains or fruits or flowers possess. We secure these properties for our uses. Gravity, sound, heat, light, electricity, chemical affinity, crystallization, even life itself, are names for certain forms of energy in nature which men are using more or less to meet their wants. Whenever exertion is needed to provide for using these, the thought of wealth is connected with the forces themselves. The fish in the sea and rivers become wealth to one who has caught them, and even more distinctly the property of the community which has protected them in breeding. Sunlight may reach all alike in welfare, but the man who has contrived to make it print pictures for him has made sunlight into wealth in the picture. Equally so the farmer's energy and contrivance use the properties of soil and climate and the vital energies of seeds to make wealth in a crop.
_Control for welfare._--As each individual worker gains control over any of these properties or forces he advances in wealth and welfare. It becomes his own means of meeting wants. If all individuals in a community share in such control, they think of the good things as part of the general welfare, and do not enumerate them in anybody's wealth except when comparing their own condition with that of another community. Advantages of this kind constantly tend to become more universal, and so to count very little in individual wealth. Many advantages of civilization today belong to all the world alike, so that nature seems to meet our wants gratuitously; but the story of progress shows that these are gifts inherited from the wealth of past ages. The human exertion which they once cost is overlooked in the ease of the present. Mere fire was once a treasure to be cherished and kept at much expenditure of strength and foresight. Now we kindle a fire so easily that nobody thinks of it as a part of the world's wealth.