15. Effects of the Suez Canal. [Fairlie; U. S. Monthly Summary, Dec., 1901.]
16. Effect of the Panama Canal on routes and traffic. [Hutchinson gives a study of results as anticipated; see U. S. Statistical Abstract and periodical literature for actual results.]
17. Development of the English postal system in the nineteenth century. [Social England, 6: 237-246; Ward, Reign of Queen Victoria, 2: 118 ff.]
18. The railroad mail service. [Amer. railway, p. 312 ff.]
19. From the figures of trade given in sect. 319 and from the figures of population in the Statesman’s Year-Book a table can be constructed giving the commerce per head of the people of different states, for comparison with the postal statistics in the text. Note, however, that these statistics include domestic mail, while figures of internal commerce are lacking. The U. S., for instance, would seem to have but slight commerce per capita, in spite of the active use of the mails, because the bulk of our trade is internal and does not appear in statistics.
20. Development of the telegraph. [Iles, chap. 13.]
21. Extension of the telegraph system in the United States. [Eckert in Depew, One hund. years, chap. 19.]
22. History of the submarine telegraph. [Iles, chap. 14; Charles Bright, The story of the Atlantic cable, N. Y., Appleton, 1903, $1; U. S. Monthly Summary, Commerce and Finance, Jan., 1899, pp. 1653-1675.]
23. Development of the telephone. [Hudson in Depew, One hundred years, chap. 20.]
24. Distribution of wireless stations. [Map in Statesman’s Year Book, 1914, plate 4.]