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mixture of yeasts, we are working with an unknown quantity. What 

 we can say therefore is this, that other conditions being favorable, 

 the fermentation and the yield will be much more regular by the use of 

 one type or variety of yeast than by the use of a mixture of yeasts. Thus 

 supposing for the sake of illustration, that we have as a mixture of yeasts 

 No. 4 and No. 18, one of which ferments in 3-4 days and the other in 

 12 ; the one producing comparatively speaking but little aroma and the 

 other producing a very strong and definite aroma, it is obvious that we 

 want the one and only the one of these two yeasts according to the re- 

 lation existing between the working capacity of oar Still House and 

 Boiling Rouse and according to the character of the rum we require to 

 produce. If in comparison to our boiling and grinding power our 

 Still House is large, we can afford to work with a slow fermentation, 

 ^nd there being no particular object then in emptying our vats quickly, 

 we should no doubt be desirous of taking advantage of the aroma- 

 producing power of Ivo. 18 yeast. Suppose that we do so desire, but 

 that instead of working with 18 yeast cultivated pure, we work with a 

 mixture of No. 18 and No 4. What guarantee have then that at some 

 future time No. 4 may not obtain the upper hand over No. 18, and that 

 instead of working with a slow aromatic fermentation, we may suddenly 

 find our "washes" attenuating with startling and unwelcome rapidity, and 

 the aroma produced by fermentation decreasing ? Or suppose exactly 

 the opposite case : that we have a large crop good boiling. and grinding 

 power, but a small Still House. Here we are forced to work with a 

 cpMck fermentation, and we desire a yeast giving a quick attenuation such 

 as furnished by No. 4 yeast. Would it not then be very inconvenient 

 to suddenly find our washes covered with a thick golden head, and lying 

 apparently " lifeless" in the vats, with the density say at 20 arnaboldi ? 

 Yet I have seen and heard of such cases occurring in Jamaica Still 

 Houses. What in one Still House may be a perfectly normal and 

 desirable fermentation may be quite abnormal and undesirable in 

 another. 



We now come to the consideration, of the second division of the subject. 

 What would be the effect of pure selected types of yeast on the quality 

 of the rum ? In other words, granting that there would be an increase 

 in the regularity of the fermentation, and in the yield of rum from a 

 given weight of sugar, and that we might produce a slow or quick fer- 

 mentation at will. Would the quality of the rum deteriorate ? Should 

 we in fact by this method manufacture not rum but spirit ? The answer 

 to this question will depend to a certain extent as to whether we are 

 working with the methods at present emplo} T ed to make " quality" rum, 

 or common or clean." 



In my second " Contribution to the Study of the Production of the 

 Aroma in Rum" which appeared in the September Bulletin, I shewed 

 that my experiments led me to believe that a preliminary " souring" in 

 the " trash" cistern was capable of playing an important part in the pro- 

 duction of the Aroma in rum. And the trash cistern has long been con- 

 sidered as a sine qua non by prrctical men in the production of high 

 flavoured rum I have already stated that yeasts exist which 

 are cajoable of influencing the aroma, and among the Jamaica yeasts 

 which I have isolated there is one No. 18 yeast, which not only in- 

 fluences the aroma in a very marked degree, but it is also capable of 



