College, and especially to Dr. R. H. Murray and Mr. G. T. Bennett, who have read the book in proof and whose criticisms upon it have been of the greatest assistance. My debt to the many writers from Whom I have quoted is apparent from the footnotes, and is particularly large in respect of the first chapter. Finally, I wish to express my deep gratitude to my colleagues at Emmanuel College Whose kindness in setting me free from the pressure of College business has enabled me.