10 HISTORY, BOTANY, ECONOMIC USES, 



Another disadvantage is the action of the sulphurous acid 

 on the tannic acid in converting it into gallic acid, which 

 prevents the clarification and the fermentation of the beers, 

 besides giving them a rough or sour flavour. The due pre- 

 servation of hops with all their active and useful properties, 

 without being subjected to sulphurous fumigation, has been 

 the object of long researches. 



Ten years ago a soft and dry extract of hops was manu- 

 factured, containing in a small volume the bitter, tonic, and 

 aromatic principles of the plant, of which it represented very 

 nearly the fifth. This soft extract is a kind of brownish pre- 

 serve, which, as it will not keep long, the brewer does not care 

 to utilize ; the dry extract which is still manufactured is in 

 a coarse powder, and keeps better ; it is used to improve the 

 bitterness of beers in course of manufacture when they are 

 too sweet. 



The question that has occupied so much time has at last 

 been solved : the preservation of hops without sulphuring 

 and without the extraction of their bitter and tannic prin- 

 ciples. By chemical and mechanical means the green or 

 freshly dried hops are separated from their essential oil, the 

 great obstacle to their preservation, so that the strobiles 

 remain whole, keep their original colour, the yellow dust at 

 the base of the scales, and all their bitter and tonic principles, 

 the aroma excepted. Hops thus treated and compressed will, 

 it is said, keep for years. 



The essential oil is preserved by itself in hermetically 

 sealed bottles, and improves from year to year. 



In the manufacture of beer, one operates with these hops 

 as usual ; and after the fermentation ten or twelve drops of 



