OK THE ART OF MAKING WINE. 19 



Gates the bitter flavour which it derives from the 

 hop, but a peculiar and nauseous taste, apparent- 

 ly derived from its ammoniacal quality. It is well 

 known to brewers, that a single spoonful of pu- 

 trid yeast, will spread its contagion through many 

 tuns of beer. If an artificial yeast is ever wanted, 

 it may be found in the lees of wine, in which it is 

 mixed with tartar, or else it may be reserved 

 from the fermentation of former parcels of domes- 

 tic wines. But a proper management of the fer- 

 mentation itself, may be made to supply the want 

 of natural leaven. I have already shown, that 

 this leaven is rendered insoluble by the act of fer- 

 mentation, and that it partly rises to the surface, 

 and partly falls to the bottom of the fermenting 

 fluid. By restoring this separated matter, the 

 process may be protracted at pleasure, till the 

 wine has acquired the degree of dry ness that may 

 be desired. It is only necessary for this purpose 

 to break the head, and disperse it through the fer- 

 menting fluid, or to agitate the whole in such a 

 way, as to mix the lees and scum with it, until the 

 desired effect is produced. The apparently ob- 

 scure process of rolling wine, or of returning it on 

 the lees to feed, as it is technically called, is found- 

 ed on this principle ; it renders the wine stronger 

 and better, by re-exciting the languid fermenta- 

 tion. The converse of this practice will be 

 equally intelligible. If a sweet wine is desired, 

 the fermenting process may be at any time artifi- 



