Foreword
Grateful acknowledgements are due to Mr. B. J. de C. Andrade, who besides supplying many diagrams read the manuscript, and made valuable suggestions; and to Mr. Godfrey Heathcote, who composed some problems especially for the book, and gave me the benefit of his expert knowledge in the writing of Chapter 10. Messrs. F. F. L. Alexander, T. R. Dawson, C. S. Kipping and J. Stewart searched their collections for anticipations, and provided me with useful data. BRIAN HARLEY
