6. Technical improvements in railroads. [See references in chap. xxx, and Johnson, chap. 4.]
7. Development of railroad organization. [Hadley, chap. 5.]
8. Contributions of railroads to industrial development. [Hatfield, Lectures, 81 ff.]
9. Freight service of the modern American railroad. [Johnson, chap. 9.]
10. Present and future of the Erie Canal. [Encyclopedia; Poole’s Index.]
11. Possible future of ship canals in the United States. [Report of the Deep Waterways Commission, House Doc. 192, 54th Cong., 2d. sess.]
12. River transportation in the Mississippi Valley. [Abbot, chap. 8; Census, 1890, Transportation by water, pp. 393-465; Report of Indust. Comm., 1900, 9: clxxxiv-clxxxviii.]
13. Place of the Great Lakes in our modern transportation system. [Tunnell; Marvin, chap. 17; Abbot, chap. 7.]
The St Mary Canal. [Tunnell; Fairlie, Ship canals, p. 67 ff.]
14. What would be the effect on lake traffic of commercial union with Canada?