I need not hazard any prediction concerning the advantages likely to accrue to the brewing industry from the adoption of such a process of brewing as my study of the subject has enabled me to devise, and from an application of the novel facts upon which this process is founded. Time is the best appraiser of scientific work, and I am not unaware that an industrial discovery rarely produces all its fruit in the hands of its first inventor. I began my researches at Clermont-Ferrand, in the laboratory, and with the help, of my friend M. Duclaux, professor of chemistry at the Faculty of Sciences of that town. I continued them in Paris, and afterwards at the great brewery of Tourtel Brothers, of Tantonville, which is admitted to be the first in France. I heartily thank these gentlemen for their extreme kindness. I owe also a public tribute of gratitude to M. Kuhn, a clever brewer of Chamalières, near Clermont-Ferrand, as well as to M. Velten, of Marseilles, and to MM. de Tassigny, of Reims, who have placed at my disposal their establishments and their products, with the most praiseworthy willingness. L. PASTEUR. PARIS, _June 1, 1876_. PREFACE TO ENGLISH EDITION. My first idea of placing before English brewers a translation of “Études sur la Bière” was meagre in the extreme, compared with the final realization of it as it appears in the following pages. Seeing the vast importance of Pasteur’s work from a practical point of view, after writing a review of it for the _Brewers’ Journal_, I determined to procure, at any rate for the use of my pupils, a literal translation, illustrated by photo-lithographic copies of the original plates, the thankless task of executing this preliminary translation for so limited a number of readers being most kindly and generously carried out for me by my friend Mr. Frank U. Waite, who, being engaged with me at the time in practical brewing operations, shared my views as to the value of the original work. It was on the completion of this translation that my views and desires expanded. The more I studied the work, the more I was convinced of its immense value to the brewer as affording him an intelligent knowledge of the processes and materials with which he deals, but over and above all this, it was impossible not to feel that the researches of such a devoted and accomplished _savant_ as Pasteur, possessed a scientific interest much wider than their mere relation to the art of brewing would imply. As the work of a skilful chemist and a laborious and accurate observer, such a protracted and careful study of the lowest and simplest forms of life, must necessarily be of first importance to the biologist—to the beginner as an admirable introduction to the study of practical physiology in general, as well as to the more advanced student, from the suggestive light which it throws on the nature of analogous phenomena in more complex organisms.