Mr. David Freeman, Mr. S. N. Fu, Mr. G. B. Gloyne, Sir Richard Gregory, Mr. F. H. Hayward, Mr. Sydney Herbert, Dr. Fr. Krupicka, Mr. H. Lang Jones, Mr. C. H. B. Laughton, Mr. B. I. Macalpin, Mr. G. H. Mair, Mr. F. S. Marvin, Mr. J. S. Mayhew, Mr. B. Stafford Morse, Professor J. L. Myres, the Hon. W. Ormsby-Gore, Sir Sydney Olivier, Mr. R. I. Pocock, Mr. J. Pringle, Mr. W. H. R. Rivers, Sir Denison Ross, Dr. E. J. Russell, Dr. Charles Singer, Mr. A. St. George Sanford, Dr. C. O. Stallybrass, Mr. G. H. Walsh, Mr. G. P. Wells, Miss Rebecca West, and Mr. George Whale have all to be thanked for help, either by reading parts of the MS. or by pointing out errors in the published parts, making suggestions, answering questions, or giving advice. The amount of friendly and sympathetic assistance the writer has received, often from very busy people, has been a quite extraordinary experience. He has met with scarcely a single instance of irritation or impatience on the part of specialists whose domains he has invaded and traversed in what must have seemed to many of them an exasperatingly impudent and superficial way. Numerous other helpful correspondents have pointed out printer's errors and minor slips in the serial publication which preceded this book edition, and they have added many useful items of information, and to those writers also the warmest thanks are due. But of course none of these generous helpers are to be held responsible for the judgments, tone, arrangement, or writing of this Outline. In the relative importance of the parts, in the moral and political implications of the story, the final decision has necessarily fallen to the writer. The problem of illustrations was a very difficult one for him, for he had had no previous experience in the production of an illustrated book. In Mr. J. F. Horrabin he has had the good fortune to find not only an illustrator but a collaborator. Mr. Horrabin has spared no pains to make this work informative and exact. His maps and drawings are a part of the text, the most vital and decorative part. Some of them, the hypothetical maps, for example, of the western world at the end of the last glacial age, during the "pluvial age" and 12,000 years ago, and the migration map of the Barbarian invaders of the Roman Empire, represent the reading and inquiry of many laborious days.