labor, capital, and the materials and motive forces afforded by nature. Of these, labor and the raw material of the globe are primary and indispensable. Natural motive powers may be called in to the assistance of labor, and are a help, but not an essential, of production. The remaining requisite, capital, is itself the product of labor. Its instru- mentality in production is therefore, in reality, that of labor in an indirect shape. Mill, Pol. Econ.; Wharton.