ON THE ART OF MAKING WINE. 



rules may appear fixed, they cannot be generally 

 applied, because, under the mutable circumstances 

 in which the application is made, they must fre- 

 quently be rendered futile, and sometimes even 

 injurious, 



The constituent parts of the fruits used in the 

 experiments now under consideration, are malic 

 acid, either in a state of purity, or one of combina- 

 tion with potash, (a circumstance not yet perfectly 

 ascertained) ; vegetable mucilage, or extractive 

 matter ; supertartrite of potash ; sugar \ water the 

 sweet principle ; the colouring principle ; tannin ; 

 super-oxalateof potash; and the principle of flavour. 

 The proportions of these, vary much in different 

 fruits, and it sometimes happens that one or more of 

 them is entirely absent. In the white currant for in- 

 stance, the colouring substance is often deficient, 

 whilst it abunds in the elder-berry and red grape. 

 So the super-oxalate of potash is rarely found ; and, 

 on the contrary, those salts to which the tartarous, or 

 malic acid appertain, are more frequent. So like- 

 wise, the sugar is much less abundant than the 

 sweet principle, which is indeed the general cause 

 of the sweetness of the greater number of our 

 fruits. The vegetable mucilage is, if any, the only 

 principle whose presence is invariable ; and this 

 principle^ is one of the most essential in the fabrica- 

 tion of a vinous liquor, as we shall see hereafter. 

 The main diversities of character, in the products 

 of the various fruits, is owing to the varying pro- 



