8 STUDIES (JN F]:ilMKNTATl()N. 



but such increase must naturally have been determined by the 

 quality of the wort, the quantity of hops used, the action of 

 oxj^geu, and the proportion of barm employed. The process of 

 fermentation lasted from three to four days. By that time the 

 beer was finished, and had become limpid, the fermentation 

 having been completed. The bungs could then be placed in 

 the casks, and the beer be delivered to the customer.* A cer- 

 tain amount of yeast still remained in the casks, and caused the 

 beer to become thick, in transit ; but a few days' rest sufficed to 

 restore its brilliancy, and render it fit for drinking or bottling. 



Here we have an explanation of the term " liigli fermenta- 

 tion," which has been applied to the foregoing process. This 

 process is conducted at a high temperature, which, commencing 

 at 19° C. or 20' C. (66° F. or 68° F.), is raised to 20° C. or 21° C. 

 (68° or 70° F.) by the action of fermentation, which is always 

 accompanied by an increase of heat.f 



* In some breweries (at Lyons especiallj') fermentation at a high tem- 

 perature is practised in largo vats at about 15' C. (59' F.). The yeast 

 which covers the surface of the liquid is skimmed off and stored in flat 

 tubs. 



t The initial temperature of the wort must be regulated bj' the 

 quantity of wort subjected to fermentation. In English breweries, where 

 large quantities are brewed at a time, the heat created by the action of 

 fermentation would produce a temperature sufficiently high to aff'ect the 

 quality of the beer, if the yeast were added at 19° C. or 20° C. 



The following are the temperatures at which the worts are pitched, in 

 the principal London breweries : — For common ale, 60' F. or 15-5° C. ; 

 for pale ale, 58° F. or 14-4" C. ; for porter, G4° F. or 17-8' C. The fer- 

 mentation is commenced in large vats ; from these the beer is run into 

 vessels of a much smaller capacity, in which it completes its fermentation 

 by working off" the yeast and cleansing itself. 



For white beer of superior qualitj^ the temperature during fennenta- 

 tion must not rise bej'^ond 72^ F. or 22*2° C. ; some brewers never allow 

 it to exceed 18° C. (()5' F.). The temperature is lowered by means of a 

 current of cold water, which circulates through a coil fixed in the vats 

 or other fermenting vessels. 



'In the case of poi-ter, the initial heat of which is 64' F. or 17 '8' C, 

 the temperature in the vats sometimes rises to 78° F. or 25"5° C. ; but 

 such an increase in temp(!rature excites considerable ajiprehension. 



We have seen a tun for pale ale, containing 200 barrels of 36 gallons, 



