Page:A Practical Treatise on Brewing (4th ed.).djvu/162

146 gyle-tun, and hence the tendency to increased acidity, when the beer is afterwards put on draught in the publican’s cellar.

There can be no doubt, therefore, that whereever the gyle-tuns are embedded in the ground, great uncertainty must accrue from the frequent electrical changes of the earth and atmosphere. The same uncertainty will exist when the gyle or fermenting tuns are lined with different metals; but when chains of pipes called mains, consisting of various metals, are connected with the gyle-tuns and cleansing casks, the positive electro-chemical action must be such as invariably to produce acidity to a certain extent during its fermentation, and thus cause the injurious effects above mentioned. This injurious effect is shown by the light yeasty heads rising to an uncontrollable extent (no close yeasty heads can ever be attained). This, however, is thought by some to be a sure indication of a fine, healthy, and vigorous fermentation; instead of which, however, it will be found that such a degree of acidity is then being generated as will prevent the beer from keeping, as it is technically called, nor can it ever arrive to be what is called really sound old—an article now as difficult to be obtained as it is much wanted.

Such are causes enough for the actual uncertainty in the quality of beer, and sufficient also to lead to the returns of those large quantities upon the