16 ON THE ART OF MAKING WINE. 1 



grape or other fruits, a portion of the leaven is 

 separated from the wine, and is exhibited in two 

 forms of yeast and lee t part rising to the surface 

 in froth, and the remainder subsiding to the bot- 

 tom of the vessel. It is essential to attend to this 

 distinction, and to understand the true nature of 

 these substances, as some of the most important 

 practices in wine-making depend on it. I must 

 add, that it still remains uncertain, whether any 

 portion, of the leaven enters into combination with 

 the vinous produce, or whether it acts solely by 

 exciting the requisite changes in the sugar, and is 

 then finally and entirely separated. The yeast 

 and lee form the artificial leaven, which, in some 

 important particulars, differs from the natural. 

 It is soluble in hot water, whereas the natural is 

 not. But it is insoluble in cold, and it is thus se- 

 parated by the act of fermentation. I may add, 

 that, notwithstanding the numerous experiments 

 to which yeast has been subjected, its composition, 

 like that of many other vegetable matters, remains 

 obscure. It is important, however, to recollect, 

 that it contains ammonia, or at least the princi- 

 ples of this substance, as Proust has shown. 

 Those who have been engaged in the manufacture 

 of domestic wines, must know, that one of the 

 most frequent defects of these wines, is an am- 

 moniacal taste ; and there is little reason to doubt, 

 that it arises from some mismanagement in the 

 process of fermentation, or an improper introduce 



