^{page 327 note 1} It should be emphasized that the comments below refer not only to the summaries, which are necessarily limited in detail and scope, but also to the larger studies generously provided me.

^{page 330 note 2} Subsequent to his earlier works on the railroads, Robert Fogel has undertaken research into this possibility for U.S. waterways in the late nineteenth century. His findings, as yet unpublished, are that marginal costs would have decreased, not increased, with enlarged water shipments.

^{page 331 note 3} Hidy, Ralph W., “The Road We Are Traveling,” THE JOURNAL OF ECONOMIC HISTORY, XXXII (March 1972), p. 5Google Scholar.

^{page 332 note 4} Donald F. Gordon, “Operational Propositions in Economic Theory,” Journal of Political Economy (April 1955), p. 160.

^{page 332 note 5} Hueckel, Glenn R., “The Napoleonic Wars and Their Impact on Factor Returns and Output Growth in England, 1793–1815,” unpublished Ph.D. dissertation, The University of Wisconsin, 1972, p. 170Google Scholar, n. 17.

^{page 334 note 1} Mauro, F.; “Towards an Intercontinental Model: European Overseas Expansion between 1500 and 1800,” The Economic History Review, XIV (1961), 1–17Google Scholar.