Alumínio, ferro e cobre em Ward (1919)

As examples of the forces that are utilized in civilization, stated in something like the historical order of their use, may be mentioned heat, light, gravitation, wind, water, steam, and electricity. The value of water as a power is in its weight, so that this is only one of the many applications of gravitation. More difficult to class, but perhaps earlier than any other, is the power of inertia in ponderable matter by which, even in the club, it is made to increase the efficiency [19] of the unaided hands. Still more subtle, but immensely effective, is the use of the principle of the lever and fulcrum, by which effects are rendered vastly greater than the muscular force exerted. These are only a few of the most obvious of nature’s powers which man learned to profit by. Of materials or substances, the simplest were wood, clay, stone, and the metals as fast as means were discovered of separating them from their ores. The reason why bronze (copper) antedates iron is that it more frequently occurs in a pure state, for it is much less abundant. Aluminum, perhaps the most abundant of all metals, was among the last to be utilized, solely because so difficult to obtain in a pure state. After these came the multitudinous chemical substances, elementary and composite, that are now applied to innumerable uses. (Ward 1919:18-9)

WARD, Lester. 1919. Pure sociology: a treatise on the origin and spontaneous development of society. New York: The Macmillan Company.