We examined with much interest the ales which had immediately preceded those undergoing fermentation, the yeast of which we had just inspected. We were furnished with two kinds, both in casks, the one fined, the other not fined. The latter was visibly turbid, and, examining a drop of it, we discovered three or four filaments present in every field of the microscope. The ale which had been fined was nearly clear, but wanting in brilliancy; it contained about one filament to the field. We asserted in the presence of the head brewer, who had been summoned, that these ales were extremely liable to change, that it was highly necessary to dispose of them without delay, and that they were necessarily already faulty in flavour—a fact which all admitted after some hesitation—attributable, of course, to the natural reluctance which every manufacturer feels to own that his produce is not above reproach. We were shown some of the finings used in the brewery; they were swarming with the same filaments of disease-organisms. We then propounded to the managers certain questions on the subject of the losses which a brewery may sustain from changes in its beer. We had heard from several brewers that the selling price of beer differed so greatly from the cost of its production solely in consequence of the losses which the unavoidable waste of large quantities of beer was constantly causing; several brewers have in our presence estimated these losses at 20 per cent. of the total production, on the average. At first the English brewers returned somewhat vague answers to our questions; however, after what had taken place, they doubtless recognized the fact that a mutual understanding between a savant and a practical man may often be of considerable benefit to the latter, and in the end they confessed to us that they had stowed away in their brewery a large quantity of beer which had gone bad in cask a fortnight or so after it was brewed. Having avowed thus much they expressed their great anxiety to learn the cause of so serious a change in their beer, which was quite undrinkable. We examined it under the microscope, without being able to detect immediately any diseased ferments, but being aware that the beer had probably been clarified, by remaining undisturbed for a very long time, and that these ferments might have become inert and precipitated to the bottom of the enormous vats containing the beer, we examined the deposits which had formed at the bottom of these vats. They were composed solely of filaments of disease-organisms, without even the least trace of the globules of alcoholic yeast. The supplementary fermentation of this beer had evidently been nothing but a diseased fermentation.