I have revised throughout the chapters Mr. Duffield left, but in doing so I have been embarrassed by the very vitality and personal quality in Mr. Duffield’s style. He reminds one of what Archdeacon Hare says of the freshness and living force in a page of Luther’s. This has constrained me to leave intact many a phrase or expression I should not have used, but which was natural and even inevitable in him. It is my hope that I have not sacrificed this admirable quality of his writing to any pedantry of judgment. The chapters on Pope Damasus (Chapter IV.) I have rewritten throughout. That on Bernard of Cluny I have rearranged, but without much alteration. That on Thomas of Celano I have rewritten to the top of page 252. That on Hermann of Reichenau I should have liked to rewrite; but as I dissented from some of its arguments, I feared to more than retouch it. It stands as a monument of its author’s vehement conviction that in Hermann he had found the true author of the _Veni Sancte Spiritus_. The later chapters, from Thomas Aquinas, with the exception of those on Jacoponus and Xavier, are the work of the editor alone. In preparing them I have followed the author’s own plan for the book, except (1) in treating of the less-known as well as the unknown hymn-writers in Chapters XXX. and XXXI.; (2) in inserting a chapter on the relations of Protestantism to Latin hymnology; and (3) in giving in the last chapter only a selection from Mr. Duffield’s great _Index of the Latin Hymns_, which I hope to see published complete in a separate book. Translations not credited to any other person are the work of Mr. Duffield. Mr. Duffield’s own idea of his book is well expressed in the Introduction which follows this Preface. I give it as he left it, although he had noted his purpose to prepare another which would cover the ground more fully. It now remains to say something of the man personally, and in this I am indebted much to the assistance of his faithful coworker in his hymnological studies, Miss Lilian B. Day of Bloomfield, who copied his great _Index of the Latin Hymns_, and who prepared the indexes to both his _English Hymns_ and the present volume.