442 Economists chief contributions are found in the Philosophy of Wealth (1886) , The Distribution of Wealth (1899), The Control of Trusts (1901), and Essentials of Economic Theory (1907). Professor Clark worked out independently the marginal utility theory of value as expounded by Jevons, Menger, and Walras, and is to be noted for the elaboration of the doctrine of specific productivity as applied to the shares of distribution. This doctrine, in con- nection with his theory of capital and his distinction between static and dynamic economics, has shed a flood of light on the recesses of economic life and has been the starting point of much modern discussion. Henry C. Adams ( 1 85 1- ) published in 1886 his Outline of Lectures upon Political Economy as well as A Study of the Principles that Should Control the Interference of the State in Industries, in which issue was squarely taken with the philosophy of laissez-faire. Later his Public Debts (1887) and the Science of Finance (1898) proved to be the pioneer American works in those fields. Richmond Mayo-Smith ( 1 854- 1901) chose the field of statistics, which he treated from the modern and comparative point of view in Statistics and Econom- ics (1888) and Statistics and Sociology (1895), as he was also the first to make a scientific study of the immigrant problem in Emigration and Immigration ( 1 890) . Richard T. Ely ( 1 854- ) , the first secretary of the American Economic Association, did perhaps more than any of the others in breaking into new fields and in popularizing the modern concepts of economics. Among his contributions may be mentioned French and German Social- ism (1883), Taxation in American States and Cities (1888), Monopolies and Trusts (1900), Outlines of Economics (1893), Studies in the Evolution of Industrial Society (1903), and Prop- erty and Contract (1914). Simon N. Patten (1852- ), in many ways the most original thinker of the group, made a series of notable contributions in The Premises of Political Economy (1885), The Economic Basis of Protection (1886), The Develop- ment of English Thought (1889), The Theory of Prosperity (1902), and The New Basis of Civilization (1907) . President A. T. Had- ley (1856- )won his spurs by a scientific study of the railroad problem in Railroad Transportation (1885), and followed this by an attempt to sum up in one volume the present state of modern thought in Economics (1896). P. W. Taussig (1859- )" started with Protection to Young Industries (1883) and followed
