\ 111 PREFACE 



and the demand on the part of many of his former students 

 for the materials which have been accumulated in his experience 

 as a teacher make it seem advisable to publish this volume 

 in its present form with the expectation that in a few years 

 the rapid development of the subject will make it possible to 

 make a much more adequate statement of the subject than is 

 here presented. 



The author wishes especially to thank Professors Richard 

 T. Ely, T. N. Carver, W. J. Spillman, and G. F. Warren, who 

 have been of great help to him from time to time, in conferences 

 and through correspondence, in clearing up many of the diffi- 

 cult problems in this field. He has also received help from time 

 to time from the succession of students who have been in his 

 classes. In leaving the classroom to enter upon activities 

 in the Government Service the author will miss the stimulus 

 which he has received from year to year through contact with 

 students. He is hoping that students who have occasion to 

 use this book will feel free to write to him in regard to any 

 of the subjects discussed in order that he may in some degree 

 continue to keep in touch with student thought on this subject. 



