Then men of genius invented improved methods of life, the building of cities and private property in lands and cattle. But gold gave power to the wealthy and destroyed the sense of contentment in simple happiness. It must always be so whenever men allow themselves to become the slaves of things which should be their dependants and instruments. They began to believe in and worship gods, because they saw in dreams shapes of preterhuman strength and beauty and deemed them immortal; and as they noted the changes of the seasons and all the wonders of the heavens, they placed their gods there and feared them when they spoke in the thunder. Metals were discovered through the burning of the woods, which caused the ores to run. Copper and brass came first and were rated above gold and silver. And then the metals took the place of hands, nails, teeth, and clubs, which had been men's earliest arms and tools. Weaving followed the discovery of the use of iron. Sowing, planting, and grafting were learnt from nature herself, and gradually the cultivation of the soil was carried farther and farther up the hills. Men learnt to sing from the birds, and to blow on pipes from the whistling of the zephyr through the reeds: and those simple tunes gave as much rustic jollity as our more elaborate tunes do now. Then, in a summary passage at the end, Lucretius enumerates all the chief discoveries which men have made in the age-long process--ships, agriculture, walled cities, laws, roads, clothes, songs, pictures, statues, and all the pleasures of life--and adds, 'these things practice and the experience of the unresting mind have taught mankind gradually as they have progressed from point to point'.[1]