Great as is the debt of gratitude which the brewing industry owes to the labours of scientific men, it has been more than repaid by the immense services which that industry has indirectly rendered to the advancement of modern science. It may be said without exaggeration that in respect of the number of scientific investigations of the first order of importance to which it has given rise, the brewing industry stands easily preeminent among the industries of mankind, and that without the stimulus furnished by the desire to arrive at the meaning of some of the more important phenomena connected with the brewing of beer, both chemical and biological science would probably be the poorer today by some of their most valued intellectual achievements. . . . The brewing of beer is regarded by many as an operation of a simple and more or less mechanical description, which is not of sufficient importance to merit study or of sufficient interest to claim a share of their attention. It is in the hope of doing something, even though it be but little, to correct this widely spread impression, that I have most willingly accepted the invitation to contribute this little work to The Cambridge Manuals of Science and Literature. From the Preface.