PREFACE

found their way into print have awakened a vigorous discussion
which is still in progress. This is well, for our science thrives on
criticism and through the collaboration of many minds the final
theory of flow will be evolved.
Without going considerably beyond the limits which we have
placed upon ourselves, it is impossible to refer even briefly to all
of the important papers on the subject. References given in
the order that they come up in the discussion are not the best
suited for later reference. The novel plan has been tried of
placing nearly all of our references in a separate appendix which
is- also an author index and is, therefore, arranged alphabetically
under the authors' names. In the text the name of the author
and the year of publication of the monograph is usually sufficient
for our purpose, but sometimes the page is also added. The titles
of the monographs are usually given in the hope that this bibli-
ography may be of considerable service to investigators who are
looking up a particular line of work connected with this general
subject.
It is a pleasure to thank Dr. R. E. Wilson of the Massachusetts
Institute of Technology and Dr. Hamilton Bradshaw of the E. I.
bu Pont de Nemours & Company for reading over the manu-
script and Dr. James Kendall for examining the proof. Profes-
sor Brander Matthews of Columbia University, Professor James
Tupper and Professor James Hopkins of Lafayette College have
assisted in important details. The author gladly acknowledges
the valuable assistance of his colleagues and co-workers, Dr.
George F. White, Dr. J. Peachy Harrison, Dr. Henry S. Van
Klooster, Mr. Walter G. Kleinspehn, Mr. Henry Green, Mr.
William L. Hyden, Mr. Landon A. Sarver, Mr. Delbert F. Brown,
Mr. Wilfred F. Temple, Mr. Herbert D. Bruce, and others.
The author is especially indebted to the University of Rich-
mond for the leisure which made possible a considerable portion
of this work.
EUGENE C. BINGHAM.
EASTON, PA.
Feb. 11, 1922.