Curtis Prout, and Miss Katherine Tyng, for valuable assistance and suggestions received during the preparation of this book. Chapter XV is largely based on an article prepared at the

PREFACE Vll

suggestion of the author by Mr. Pierpont V. Davis of New York City and pubUshed by Mr. Davis in Moody's Magazine. I wish also to express my thanks to numerous friends who have given excellent suggestions and criticisms during the time the manuscript was in preparation.

If this book should receive any commendation, much of that commendation will be the result of good fortune in securing an unusually high grade of drafting skill on those charts which are original.

The author cannot be responsible for the accuracy of the data presented in many of the charts shown. The illustrations have been selected partly on account of the educational value of the facts, but chiefly because of the methods used in presentation. Though great care has been exercised to make the titles complete, the elaboration of titles beyond their wording in the original source may have resulted in some inaccuracies.

As far as the author is aware, there is no book published in any language covering the field which it has been attempted to cover here. If the presentation of the subject appears to be crude and incomplete, it is hoped that any critic will keep in mind that there is httle precedent for guidance in a territory so unexplored.

It is impossible entirely to avoid errors in any book containing as much detail as results here from the numerous complex illustrations and the necessity of carefully worded language to give condensed information. Any corrections, criticisms or suggestions will be appreciated by the author.