RESULTS OF SCIENTIFIC RESEARCH IN PRACTICE. 215 



in the well-known Old Carlsberg brewery at Copenhagen 

 employed in numerous breweries in all beer-producing 

 countries, not only in Europe, but also in America, Asia, 

 and Australia. 



Since Hansen's system was first carried out in a bottom- 

 fermentation brewery, it naturally first found application 

 in breweries of the same kind, and it is here that it has 

 reached the highest degree of perfection. Any one who 

 wishes to become acquainted with ike application of this 

 system to one or the other branch of the fermentation 

 industries, should therefore take as the starting-point of 

 his studies the results achieved in bottom-fermentation 

 brewing. 



The advance was subsequently introduced into top- 

 fer 'mentation brewing, and it was found that here also 

 the system offers the same advantages. At first the same 

 objection was again raised which had been brought forward 

 against pure cultivations of bottom-yeast, namely, that it 

 could not produce a secondary fermentation, as the latter 

 was supposed to be caused by the so-called wild species of 

 yeast; the objection, however, again fell through when the 

 question was submitted to the practical test of experiment. 

 There are, in fact, top-fermentation yeasts which give 

 a vigorous secondary fermentation, and others which 

 produce only a feeble after-fermentation. A species should 

 therefore be systematically selected which will answer the 

 required conditions. 



The new system afterwards continually spread, and has 

 now forced its way into distilleries, pressed-yeast factories, 

 and into the different vinous fermentations. 



Hansen's epoch-making investigations of the last decade 

 have given rise to a very extensive literature, the contents 

 of which may be summed up under three headings : 

 Treatises of a purely ephemeral nature, the only object of 

 which is clearly to oppose the work of the Danish investi- 

 gator and to bring obstacles against the introduction of 



