During Mr. Little's absence in China, the proofs of this book were kindly read for me by my colleague at the London School of Economics, Mr. A. J. Sargent, to whom my thanks are due. Mr. Little returned in time to see the last revise.

The maps and diagrams in the text have been prepared by Mr. A. W. Andrews of the Diagram Company, to whom and to Mr. J. G. Bartholomew, who executed the coloured maps, my thanks are also due.