392 STUDIES ON FKRMENTATION. 



moment when it is drawn off, is, in the case of all beers, the 

 yeast of a supplementary fermentation, if we may use that 

 expression. In the ordinary process of brewing, this yeast, in 

 consequence of the greater aeration of the wort at the com- 

 mencement of fermentation, is more active, or, rather, more 

 ready to revive and multiply than is that which develops in 

 closed vessels. If the barrels of the K beer had been tapped 

 on the 12th or 15th of November, instead of on the 3rd, it is 

 probable that they would have contained as much carbonic acid 

 gas as the beer M contained at the earlier date. This delay in 

 the resumption of fermentation, which characterizes beer made 

 in closed vessels, is an advantage, inasmuch as it facilitates the 

 transmission of the beer to long distances, besides giving us the 

 smallest deposits of yeast in cask or bottle, as we have already 

 pointed out. 



In comparing the keeping qualities of the beer M and the 

 beer T (the latter being the brewery beer), we made the follow- 

 ing observations : — * 



On November 25th we began to detect in the brewery beer 

 an unsound flavour ; a large deposit, too, had formed ; the beer 

 had lost its brilliancy, and frothed enormously. The deposit 

 swarmed with diseased ferments, especially those represented in 

 Nos. 1 and 7 of Plate I. The beer M, on the contrary, was in 

 brilliant condition, with an insignificant deposit, and an ordi- 

 nary froth, if anything, rather small, and beautifully bright. 



On December 3rd the beer M was still good, very clear, and 

 in excellent preservation ; it was considered by professional 

 brewers as remarkably sound. 



December 22nd, the same beer M was still very bright and 

 good. 



January 20th, the beer was still bright ; for the first time, 

 however, we detected in the deposit in the bottles, which was 

 otill small, the filaments of turned beer. This unsoundness was 



* One of the barrels of the brewery beer was bottled about the end of 

 October, at the same time that a barrel of M was. 



