I determined accordingly _to publish_ the work if I could secure the consent of its distinguished author, but at the same time I felt that the publication of M. Pasteur’s “Studies” in the form in which Mr. Waite had, at my request, translated it, and illustrated only with inferior copies of the original plates, would not be either advisable or just; but that I was bound rather to put the book before the English public in as satisfactory and complete a form as lay within my power. Under these circumstances I was induced to seek the aid of Mr. D. Constable Robb, B.A., of The Oxford University Museum, who, in taking Mr. Waite’s version as a basis, has so elaborated, annotated, and recast it, that I feel bound to say that much of the value of “Studies on Fermentation,” as it now appears, is due to the care that Mr. Robb has bestowed upon the revision that he so kindly undertook; a revision the result of which has created a feeling of confidence in the success of the translation as it now stands, which I could not have had in any mere literal version. To the practical worker the original illustrations alone, which appear in this version, cannot but be of immense value in the microscopical study of the changes in the liquids with which he deals; whilst the many notes and additions, which are a feature peculiar to the English edition, more particularly the rendering into the equivalents, with which, unfortunately, practical men on this side of the channel are still most at home, of the metric weights and measures and centigrade temperatures, as well as the Index which Mr. Robb has compiled, will, I trust, render the book of still greater service than it otherwise would have been to many of those who may favour it with their attention. The debt which we English brewers owe to M. Pasteur can hardly be over-estimated, and I must be allowed here to express my personal obligations to that distinguished worker for the permission which allows this translation; and to the French publishers for their help with regard to the interleaved illustrations. The author’s preface and dedication are, of course, reproduced, the former making it unnecessary for me to refer more in detail to the contents of the translation. FRANK FAULKNER. THE BREWERY, ST. HELEN’S, LANCASHIRE, _September, 1879_. TABLE OF CONTENTS. AUTHOR’S DEDICATION v AUTHOR'S PREFACE vii TRANSLATOR’S PREFACE ix CHAPTER I. ON THE INTIMATE RELATION EXISTING BETWEEN THE DETERIORATION OF BEER, OR THE WORT FROM WHICH IT IS MADE, AND THE PROCESS OF BREWING 1 CHAPTER II. ON THE CAUSES OF THE DISEASES WHICH AFFECT BEER AND WORT. § I. Every unhealthy change in the quality of beer coincides with a development of microscopic germs which are alien to the pure ferment of beer 19 § II. The absence of change in wort and beer coincides with the absence of foreign organisms 25 CHAPTER III. ON THE ORIGIN OF FERMENTS PROPERLY SO CALLED.