FERMENTATION. 241 



being changed by fermentation, it will become in time sour 

 or putrid, according to the nature of the body upon which 

 it acts. 



Generally speaking, the French grapes when ripe contain 

 such proportions of sugar and the vegeto-animal principle 

 as are well adapted for producing the vinous fermentation ; 

 but when the summer is cold or damp, the proportion of 

 sugar is less, and the predominance of the mucilage renders 

 the liquor weak. In this case, the small quantity of alcohol 

 which is developed is not sufficient to preserve the wine 

 from spontaneous decomposition, and at the return of heat, 

 a new fermentation takes place, the product of which is 

 vinegar. This evil may be easily obviated by artificial 

 means : it is only necessary to add to the liquor such a quan- 

 tity of sugar as would naturally have been found in it, under 

 usual circumstances. 



For ascertaining the quantity of sugar which belongs to 

 the must of well-ripened grapes, the following hints will be 

 sufficient. 



In the south of France, the grapes usually arrive at a state 

 of perfect maturity, and if the fermentation be well conduct- 

 ed, the wine will keep well ; but in the north, however fa- 

 vorable the season may be, the grapes never become perfect- 

 ly ripe. I have always observed that the wine of the south, 

 which had been well fermented, marked upon the aerometer 

 some fractions of a degree below the specific gravity of wa- 

 ter, whilst the new wines of the north rarely cause the 

 aerometer to descend to the same degree. 



Another important circumstance by which we must be 

 guided in ascertaining the quantity of sugar necessary to be 

 employed, is the degree of concentration of the must : this 

 varies with every vintage, and the aerometer has often indi- 

 cated to me a difference of concentration, varying from 2" 

 to 4° (zz: specific gravity of 1.014 to 1.029,) in the must 

 procured from the same vineyard, according to the state of 

 ripeness which the fruit had acquired ; the heaviest must be- 

 ing furnished by the ripest grapes. 



In Touraine, and upon the borders of the Cher and the 

 Loire, the weight of the must varies from 8.5° to 11°; 

 {=. specific gravity of 1.063 to 1.083.) I have observed it 

 in the south to range between 10° and 16° (r= specific 

 gravity of 1.075 to 1.125.) Having once ascertained the 

 specific gravity of the must obtained fi"om perfectly ripe 

 grapes, it is only necessary to bring to the same weight, by 

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