When we review the operations of the brewer’s art, we are surprised by the comparative perfection to which that art has been brought by the laborious experience of years, and the more so when we consider that, as regards the question of the diseases of beer, the brewer has never been guided by any such rigorous principles as those which we have explained in this work. We have already given proofs of this in our first chapter. The beer is racked and separated from its yeast before fermentation has entirely ceased. The principal reason for this is that it is necessary that the beer, after being run into cask, should work again and undergo a secondary fermentation, in order that it may not be invaded by the parasites, of which we have already spoken, as would not fail to be the case if the beer were suffered to remain in a state of perfect quiescence. Not only is the beer racked before it has attained its limit of attenuation, but in addition to this, and also with the view of checking the development of parasites, it is placed in cellars sensibly cooler than the temperature of fermentation, low as that is in the case of “low” beers: the temperature of the cellars being not higher than 2° or 3° C. (36° F.). Unfortunately, the requirements of trade prevent our complying with these exigencies to the end. When the beer is sold it is conveyed away, no matter what the season may be, and deposited in the retailer’s cellar, for a longer or shorter time, according to the variations of consumption. On a warm day beer will be in great demand; the next day, if rain or cold have come on, the demand will be very limited, since beer is, in our climate at least, a drink for hot weather. From causes of this nature, the beer may have to remain a long time in the cellars of the retailers or consumers. By way of precaution, indeed, it is put into very small casks, which permit of a frequent renewal of the supply, and is conveyed to distances by express trains, and during the night; it is even sent away in wagons provided with a kind of double case, the outer jacket being filled with ice, which keeps the air surrounding the casks constantly cold. Such are some of the troublesome measures taken to obviate the danger that we have pointed out. They operate very injuriously in restricting the trade and raising the price of beer. It is a matter of extreme importance, then, that our produce should be better removed from the action of those microscopic enemies which beer contains; in other words, that this beverage should have less cause to fear circumstances favourable to the development of the germs of impurity with which it is always contaminated, as a natural consequence of the methods of manufacture at present adopted. The question of alteration in the flavour of beer should be regarded from another point of view which merits equal attention. We have seen that there are different kinds of beer, each of which corresponds to a special ferment