VI 



PREFACE 



Professor E. W. Lane assisted in the preparation of Chapter IX and 

 read the entire manuscript, giving much valuable advice. Mr. J. C. 

 Stevens read the manuscript and made many worth-while suggestions. 

 The late Professor Floyd A. Nagler and the late David L. Yarnell 

 assisted in the development of some of the subject matter that appears 

 here for the first time. In the course of classroom discussion many of the 

 authors' students have made contributions which are incorporated in the 

 text. To all who have helped directly, and to the many contributors to 

 the literature whose efforts have been drawn upon, the authors wish to 

 express their sincere appreciation. Finally, they wish to thank the staff 

 of John Wiley and Sons for its fine cooperation in preparing the manu- 

 script for the press. 



Sherman M. Woodward 

 Chesley J. Posey 



September, 1941 



