b THE GKAPE. 



therefore, equally formed in the skin, and dissolved in 

 equal quantity in the wine ; so that, in general, the 

 more the red wines contain of colourless tannic acid, 

 the darker they will be, that is, the more do they hold 

 in solution of the colouring matter of the purple 

 skins. 



It is, therefore, possible to prepare lighter or darker 

 coloured red wines, and to impart to them more or 

 less tannic acid in proportion to the greater or 

 smaller quantity of purple skins allowed to ferment 

 with their juice. 



As we shall have occasion hereafter to treat in 

 detail of the colouring matters and of the tannic acid, 

 we will only mention here, that the first are always 

 simple ; it is a blue matter, which, by means of the 

 free acids of the wine, acquires a peculiar reddish 

 colour. What other matters can be extracted from 

 the skins, when these are allowed to ferment with the 

 juice, is not known, but it is certain that the tannic 

 acid in wine is derived principally from the skin ; so 

 that such wines as are prepared from fermented juice 

 alone, without any admixture of skins, contain either 

 none, or at best only a doubtful trace of its presence. 



If the skins are allowed to ferment, the grape 

 stones will not be excluded from fermentation, for in 

 general one may take it for granted that an incom- 

 plete filtration of the expressed fluid will allow a large 

 number of grape stones, richly provided with tannic 

 acid, to ferment with it. 



