1. Minor changes have been made to correct typesetters' errors, and to ensure consistent spelling and punctuation in this etext; otherwise, every effort has been made to remain true to the original book. 2. The chapter summaries in this text were originally published as banners in the page headers, and have been moved to beginning of the chapter for the reader's convenience. 3. Typesetting for italics was very inconsistent in this book; no attempt has been made to regularize the use of italics.