672 THE POPULAR SCIENCE MONTHLY. 



panied with a corresponding variation in the chemical composition of 

 any particular class of grapes, but somehow the wine produced there- 

 from obeys the laws of supply and demand. For some years past the 

 demand for dry sherry has dominated in this country, though, as I am 

 informed, the weathercock of fashion is now on the turn. 



One mode of satisfying this demand for dry wine is, of course, to 

 select a grape which has less sugar and more albuminous matter, but 

 in a given district this is not always possible. Another is to gather 

 the grapes before they are fully ripened, but this involves a sacrifice 

 in the yield of alcohol, and probably of flavor. Another method, 

 obvious enough to the chemist, is to add as much albuminous or nitro- 

 genous material as shall continue to feed the yeast-fungus until all, 

 or nearly all, the sugar in the grape shall be converted into alcohol, 

 thus supplying strength and dryness (or salinity) simultaneously. 

 Should these be excessive, the remedy is simple and cheap wherever 

 water abounds. It should be noted that the quantity of sugar natu- 

 rally contained in the ripe grape varies from ten to thirty per cent — 

 a very large range. The quantity of alcohol varies proportionally 

 when the must is fermented to dryness. According to Pavy, "there 

 are dry sherries to be met with that are free from sugar," while in 

 other wines the quantity of remaining sugar amounts to as much as 

 twenty per cent. 



White of egg, and gelatine are the most easily available and inno- 

 cent forms of nitrogenous material that may be used for sustaining or 

 renewing the fermentation of wines that are to be artificially dried. 

 My inquiries in the trade lead me to conclude that this is not under- 

 stood as well as it should be. Both white of egg and gelatine (in the 

 form of isinglass or otherwise) are freely used for fining, and it is 

 well enough known that wines that have been freely subjected to such 

 fining keep better and become drier with age, but I have never yet 

 met a wine-merchant who understood why, nor any sound explanation 

 of the fact in the trade literature.* When thus added to the wine 

 already fermented, the effect is doubtless due to the promotion of a 

 slow, secondary fermentation. The bulk of the gelatine or albumen is 

 carried down with the sediment, but some remains in solution. There 

 may be some doubt as to the albumen thus remaining, but none con- 

 cerning the gelatine, which is freely soluble both in water and alcohol. 

 The truly scientific mode of applying this principle would be to add 

 the nitrogenous material to the must. 



I dwell thus upon this, because, if fashion insists so imperatively 

 upon dryness as to compel artificial drying, this method is the least 

 objectionable, being a close imitation of natural drying, almost identi- 

 cal ; while there are other methods of inducing fictitious dryness that 

 are mischievous adulterations. 



* The wine-trade has two rival magazines, both very high-priced, exclusively devoted 

 to its interests, besides others that are partially so. 



