There was a brewery at Chamalières, between Clermont and Royat. Pasteur began by visiting it with eager curiosity, inquiring into the minutest details, endeavouring to find out the why and the wherefore of every process, and receiving vague answers with much astonishment. M. Kuhn, the Chamalières brewer, did not know much more about beer than did his fellow brewers in general. Very little was known at that time about the way it was produced; when brewers received complaints from their customers, they procured yeast from a fresh source. In a book of reference which was then much in use, entitled _Alimentary Substances: the Means of Improving and Preserving them, and of Recognizing their Alterations_, six pages were given up to beer by the author, M. Payen, a member of the Institute. He merely showed that germinated barley, called malt, was diluted, then heated and mixed with hops, thus forming beer-wort, which was submitted, when cold, to alcoholic fermentation through the yeast added to the above liquid. M. Payen conceded to beer some nutritive properties, but added, a little disdainfully, “Beer, perhaps on account of the pungent smell of hops, does not seem endowed with stimulating properties as agreeable, or as likely to inspire such bright and cheerful ideas, as the sweet and varied aroma of the good wines of France.” In a paragraph on the alterations of beer--“_spontaneous_ alterations”--M. Payen said that it was chiefly during the summer that beer became altered. “It becomes acid, and even noticeably putrid, and ceases to be fit to drink.” Pasteur’s hopes of making French beer capable of competing with German beer were much strengthened by faith in his own method. He had, by experimental proof, destroyed the theory of spontaneous generation; he had shown that chance has no share in fermentations; the animated nature and the specific characteristics of those ferments, the methods of culture in appropriate media, were so many scientific points gained. The difficulties which remained to be solved were the question of pure yeast and the search for the causes of alteration which make beer thick, acid, sour, slimy or putrid. Pasteur thought that these alterations were probably due to the development of germs in the air, in the water, or on the surface of the numerous utensils used in a brewery. As he advanced further and further into that domain of the infinitely small which he had discovered, whether the subject was wine, vinegar, or silkworms--this last study already opening before him glimpses of light on human pathology--new and unexpected visions rose before his sight.