INTRODUCTORY. 



NEARLY a century has elapsed since the constituents of the hop 

 cone first attracted the attention of Chemists, and the fact that 

 we are only now beginning to understand the principal chemical 

 characters of some of those constituents and the roles they play in 

 the brewing process, is in itself the strongest evidence of the 

 magnitude of the difficulties which have been encountered. Seeing 

 that the constituents in question (resins, bitter principles, essential 

 oil, tannin, &c.) are among the most complicated substances with 

 which the Chemist has to deal, it is not surprising that the older 

 investigators were, as a rule, very wide of the mark, and that many 

 of the earlier statements were hopelessly incorrect. During the 

 past decade a number of Chemists have devoted attention to the 

 investigation of the more important hop constituents, with the result 

 that a great deal of definite information has been gained and many 

 of the old errors cleared away. Nor has the knowledge thus 

 acquired been merely of scientific interest, for it has thrown much 

 light on the part played by the hop in the manufacture of our 

 national beverage, and has already found industrial application to 

 the great advantage both of the hop- growing and of the brewing 

 industries. That there is much that is still doubtful and obscure is 

 unfortunately true, but the rapid progress which has been made 

 during recent years justifies the hope that before very long the 

 existing gaps in our knowledge will be filled. About a year ago 

 the Management of the Brewing Trade Review conceived the idea of 

 publishing a series of articles dealing with the Chemistry and 

 Natural History of the Hop Plant, each article to be written as far as 

 possible by someone possessing special knowledge of the particular 



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