FERMENTATION 269 



placed in proper vessels, and abandoned to its own action. 

 It ferments, producing carbonic acid; its sweetness disap- 

 pears, and at the end of a certain time the unintoxicating 

 grape-juice is converted into intoxicating wine. Here, as 

 in the case of the cherries, the fermentation is spontaneous 

 in what sense spontaneous will appear more clearly by 

 and by. 



It is needless for me to tell a Glasgow audience that 

 the beer- brewer does not set to work in this way. In the 

 first place the brewer deals not with the juice of fruits, 

 but with the juice of barley. The barley having been 

 steeped for a sufficient time in water, it is drained and 

 subjected to a temperature sufficient to cause the moist 

 grain to germinate ; after which it is completely dried upon 

 a kiln. It then receives the name of malt. The malt is 

 crisp to the teeth, and decidedly sweeter to the taste than 

 the original barley. It is ground, mashed up in warm 

 water, then boiled with hops until all the soluble portions 

 have been extracted; the infusion thus produced being 

 called the wort. This is drawn off, and cooled as rapidly 

 as possible; then, instead of abandoning the infusion, as 

 the wine-maker does, to its own action, the brewer mixes 

 yeast with his wort, and places it in vessels each with 

 only one aperture open to the air. Soon after the addi- 

 tion of the yeast, a brownish froth, which is really new 

 yeast, issues from the aperture, and falls like a cataract 

 into troughs prepared to receive it. This frothing and 

 foaming of the wort is a proof that the fermentation is 

 active. 



Whence comes the yeast which issues so copiously 

 from the fermenting tub? What is this yeast, and how 

 did the brewer become possessed of it? Examine ita 



