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From the conception of mechanical force as coming in from Nature to the service of man, a conception the Utopian proposal of a coinage based on energy units would emphasise, arise profound contrasts between the modern and the classical Utopias. Except for a meagre use of water power for milling, and the wind for sailing—so meagre in the latter case that the classical world never contrived to do without the galley slave—and a certain restricted help from oxen in ploughing, and from horses in locomotion, all the energy that sustained the old-fashioned State was derived from the muscular exertion of toiling men. They ran their world by hand. Continual bodily labour was a condition of social existence. It is only with the coming of coal burning, of abundant iron and steel, and of scientific
