464 THE BREWING INDUSTRY IN IRELAND. 



alcoholic gas, appearing as a bluish vapour over the surface of 

 the yeast. The carbonic acid gas may be pumped off from the 

 fermenting vessels and collected for compression. It forms a 

 valuable bye-product, but the process of securing it is elaborate and 

 profitable only in very large breweries. In the year 1 890 Messrs. 

 Arthur Guinness, Son and Co. first began to utilise the acid given 

 off. It may be used in the artificial production of cold {e.g., for the 

 refrigerators required in the brewery) and it may be reduced to a 

 liquid state in which condition it is sold in steel cylinders for the 

 purpose of soda water manufacture, cooling machines, etc. The 

 freight upon the cylinders is, however, very heavy, and the demand 

 for carbonic acid in the United Kingdom is not very extensive, 

 and consequently it does not form a sufficiently remunerative bye- 

 product to induce most brewers to work it up. 



Simply stated, the effect of fermentation is to change a portion 

 of the saccharine in the worts into alcohol, and the longer the fer- 

 mentation is allowed to go on, the greater will be the change. In 

 the case of pale ales which are comparatively highly alcoholic, and 

 in the case of ales for export, which require keeping qualities, the 

 fermentation, or attenuation as it is called, is allowed to proceed 

 much further and longer than when mild ale or porter for im- 

 mediate consumption is being brewed. 



During fermentation the worts throw off a quantity of yeast, 

 which rises to the top of the liquor and is constantly skimmed off 

 and forms a bye-product. Sometimes it is sold in the liquid state 

 in which it was removed, and is then known as barm ; in other 

 cases it is pressed and made into solid yeast cakes, and the liquor 

 pressed out can be worked up afterwards. In large breweries the 

 surplus yeast not required for producing fermentation in the 

 brewery, is pumped by hydraulic pressure through machines fitted 

 with swansdown bags, until it assumes the consistency of soft 

 cheese, after which it is packed into bags and sold to distillers. 

 (6) When the fermentation has proceeded far enough, the remnants of 

 the yeast are removed and the beer is cleansed, cleared, and 

 sent on to the fining or storage vessels, the temperature, which 

 during the fermenting process has ranged up to 70° F., being 

 brought to the normal state of from 58° to 60° F. The beer is now 

 ready to be stored or put into casks according as it is intended for 

 export or for immediate consumption, and according to the nature 

 and quality of the drink. 



As most of the liquor brewed in Irish breweries ii of the class known as 



porter, a few words concerning this article may not be out of place. 



Porter differs from ale in several respects, and especially in the fact that 



it contains a greater amount of nutritive matter, and a 



Porter considerably less proportion of alcohol. Its origin 



dates back to 1722, when porter was first brewed by 



Harwood, a London brewer, who gave it the name 



of " Entire." This expression " Entire " requires some explanation. At 



the date referred to the beer retailers had a custom of selling a beverage 



called " half and half," i.e., half ale and half " twopenny " (another kind of 



beer), which had to be drawn from two casks. The pubHc at a later period 



