286 GRAPE CULTURE AND 



assists the evaporation. That the latter is accompanied by 

 its transformation into vinegar is apparent to the nostrils so 

 soon as the first violent stage of the fermentation is past. 



In the case of the "Morel process" the cause of the loss of 

 alcohol is not so obvious. It might be accounted for by the 

 abundant stirring and high temperature, and, doubtless, this 

 contributes to the evaporation, so much the more as the 

 terns, more or less emerged above the surface, afford better 

 opportunity than a cap formed of skins alone. Yet the loss 

 appears to be greater than can be accounted for on this basis 

 alone, for the reason that in No. 560, where thefoufagf was 

 nearly as diligent as in the "Morel" tank, and which was also 

 open to the air, the alcohol percentage is not sensibly dimin- 

 ished. It is possible that from some cause a part of the sugar 

 may have been converted into some other compound than al- 

 cohol ; among these, glycerine suggests itself, but the deter- 

 mination of this substance in the wines has not yet been made. 



A somewhat unexpected result is the fact that the two hot 

 fermentations (556 and 557) yielded the same amount of al- 

 cohol as those fermented at a much lower temperature. The 

 obvious explanation is, that the short duration of these fer- 

 mentations balanced the influence of the high temperature as 

 compared with those in the slower fermentations, in which 

 the opportunity for evaporation lasted longer. It will be highly 

 interesting to compare, hereafter, the other products formed 

 alongside of the alcohol in the three sets of fermentations. 



ACID. 



As regards, next, the acid of the several wines, it is not un- 

 expected to find that the openfou/age, No. 560, on the one 

 hand, and the Morel process on the other, having given the 

 highest' figure, the one because of the constant access of air, 

 the other from the same cause, in addition to the extraction 

 of acid from the stems. 



