OILY AND ETHEREAL PRODUCTS. 287 



such as the Riessling and Orleans, have the strongest 

 perfume or bouquet, and contain, proportionally, a 

 larger quantity of tartaric acid. The earlier grapes, 

 such as the Rulander, and others, contain a large 

 proportion of alcohol, and are similar to Spanish 

 wines in their flavour, but they possess no bouquet. 



The grapes grown at the Cape from Riesslings 

 transplanted from the Rhine, produce an excellent 

 wine, which does not however possess the aroma 

 which distinguishes Rhenish wine. 



It is evident from these facts, that the acid of 

 wines, and their characteristic perfumes, have some 

 connexion, for they are always found together, and 

 it can scarcely be doubted that the presence of the 

 former exercises a certain influence on the forma- 

 tion of the latter. This influence is very plainly 

 observed in the fermentation of liquids, which are 

 quite free from tartaric acid, and particularly of 

 those which are nearly neutral or alkaline, such 

 as the mash* of potatoes or corn. 



The brandy obtained from corn and potatoes 

 contains an ethereal oil of a similar composition 

 in both, to which these liquors owe their peculiar 

 smell. This oil is generated during the fermenta- 

 tion of the mash ; it exists ready formed in the fer- 

 mented liquids, and distils over with alcohol, when 

 a gentle heat is applied. 



It is observed that a greater quantity of alcohol 



* Mash is the mixture of malt, potatoes, and water, in the mash tun, 

 a large vessel in which it is infused. TRANS. 



