STUDIES ON FERMENTATION. 7 



During the lust thirty years, or so, the art of brewing has 

 undergone a radical change, at least in Europe. This change 

 has been effected by a partial abandonment of the process of 

 fermentation formerly used. Thirty years ago only one kind 

 of beer \Vas known ; there are nowadays two distinct kinds — 

 beer fermented at a high temperature, and beer fermented at a 

 low temperature. Each of these is subdivided into many varieties, 

 to which different names are given, according to their strength 

 or colour. This is the case in England, where we find porter, 

 ale, pale ale, stout, bitter beer, and other varieties of beer, 

 although, as a matter of fact, the English have but one kind of 

 beer, all the English beers being fermented at a high tem- 

 perature. 



Let us briefly examine tlie diflPerences existing between the 

 two kinds of beer. 



Formerly all beer was fermented at a high temperature. The 

 wort, after having been cooled in the backs, was run into a 

 large vat, at a temperature of about 20° C. (68° F.). Yeast 

 was then added to it, and when the fermentation began to show 

 itself, in the formation of a light, white froth, upon the surface 

 of the liquid, the wort was run into casks, having a capacity 

 of from 50 to 100 litres (11 to 22 gallons) — 75 litres being the 

 commonest size. These casks were placed in cellars, having a 

 temperature of from 18° C. to 20° C. (64° F. to 68° F.). The 

 activity of fermentation soon produced a froth that grew thicker 

 and more and more viscous in proportion to the quantity of 

 yeast it contained. The yeast worked out of the bung-holes 

 and dropped into a vessel placed under the casks ; there it was 

 gathered for subsequent operations. It alwaj^s exceeded the 

 quantity used in the first instance, the ferment increasing 

 greatly during the process of fermentation. The increase in 

 its weight varied with the weight of yeast used and the com- 

 position of the wort. Under the ordinary conditions of brewing, 

 where the weight of the pitching yeast was about one thou- 

 sandth part of the weight of the wort, the increase is said to 

 have been from five to seven times the weight of the yeast ; 



