For carefully studied accounts of ocean transportation in its different aspects see Joseph R. Smith, *Organization of ocean commerce, Boston, 1905, The ocean carrier, by the same author, N. Y., 1908, and Emory R. Johnson and G. G. Huebner, *Principles of ocean transportation, N. Y., 1919. These books offer bibliographies which may be used to supplement references here given. On the development of sailing ships, beside the older books by Lindsay and Cornewall-Jones, see Adam W. Kirkaldy, British shipping, London, 1914, A. H. Clark, The clipper ship era, 1911, books by Basil Lubbock on ships of the clipper period, and references given later for American shipping; on steamships there are satisfactory accounts in Fry and Maginnis and in the collection entitled Ocean steamships. Excellent chapters on the different ship canals, with further references, are given in Johnson and Huebner. See also Lincoln Hutchinson, The Panama Canal, N. Y., 1915. Summary accounts of the development of the postal service, satisfactory for the purposes of most readers of this book, will be found in the encyclopedias. A scholarly study of the development, particularly in the first half of the nineteenth century, is provided by J. C. Hemmeon, History of the British post office, Cambridge, Harvard University, 1912. The various applications of electricity are fully treated by Iles. Other books aiming to describe electrical applications for the general public are by Tunzelmann in the Contemporary Science Series, Park Benjamin, and Philip Atkinson. Consult the A. L. A. Catalogue for further references. CHAPTER XXXII THE WARES OF COMMERCE =371. Effect on commerce of technical progress.=—It is now time to discuss the effects on commerce of the technical changes which have been described in preceding chapters. Following back the substance of those chapters, the effects may be briefly summarized as follows. First, an improvement in the means of communication and transportation which has brought men and goods of different regions vastly nearer to each other than they have ever been before in the world’s history. Second, a control over the forces and materials of nature which has enabled men to manufacture old wares more cheaply and new wares which were before unknown. Third, as a result of the development of the transportation system, the settlement of new countries with virgin soil and rich mineral resources, and the connection of these countries with each other and with the countries of the Old World.