BREWING. 159 



From the coolers the wort is put into the "work- 

 ing tun, in which it is mixed with yeast, in the 

 proportion of a gallon to four barrels of wort, in order 

 to excite the vinous fermentation. This process is 

 called tunning. By this the beer obtains its strength 

 and spirit ; the sugar extracted from the malt being 

 con\^erted into alkohol. In four or five hours the 

 fermentation begins. Its first appearance is by a 

 white line on the surface of the liquor, next to the 

 side of the vessel, which gradually advances to the 

 middle, till the w^hole surface is covered with a 

 scum, or froth, formed by innumerable minute 

 bubbles of carbonic acid gas, which rise through the 

 liquor. The temperature of the liquor increases, 

 and the whole is much agitated. The froth on the 

 surface accumulates, and constitutes the yeast. At 

 this time the presence of carbonic acid gas may be 

 easily perceived, by holding one's head over the 

 barrel or tun ; and fatal accidents have happened 

 through the accumulation of this gas in situations 

 where persons have been exposed to it without 

 being able to remove. 



The vinous fermentation must be checked in 

 time, otherwise the acetous fermentation would 

 begin ; all the spirit would be lost, and the beer 

 would become sour. 



The fermentation requires from 18 or 20 to 48 

 hours J and the beer is then put into smaller barrels, 

 called cleansing tuns. In them, the fermentation 

 goes on again, and during a fev/ days, a copious 

 discharge of yeast takes place from the bung-hole. 

 Care must be taken that the barrels are filled every 

 day with fresh liquor. This discharge gradually 

 becomes less, and in about a week it ceases j when 

 the bung-hole is closed. 



The liquor is now suffered to stand for some 



