a?id the Method of making Wines, 329 



The air, no doubt, is favourable to fermentation. This 

 truth seems established by a concurrence of all the facts 

 known : for, when preserved from the contact of the air, 

 must will keep a long time without any change or alteration. 

 But it is proved also, that thougli must shut up in close vessels 

 undergoes very slowly the pheenomena of fermentation, it at 

 length terminates, and that the wine produced by it is more 

 generous. This is the result of the experimets of D. Gentil. 



If a little yeast of beer and melasses, diluted in water, be 

 introduced into a flask with a bent beak, and if the beak of 

 the flask be opened under a bell filled with water, and inverted 

 over a pneumatic tub, at the temperature of 60 or 65 degrees ; 

 Recording to my observations, the first phaenomena of fer- 

 mentation will always appear a few minutes after the appa- 

 ratus has been thus arranged ; the vacuum of the flask soon 

 becomes filled with bubbles and foam; a great deal of car- 

 bonic acid passes under the bell ; and this movement does 

 not cease till the liquor has become spiritous. In no case 

 have I ever seen an absorption of atmospheric air. 



If, instead of giving free vent to the gaseous matters which 

 escape by the process of fermentation, their disengagement 

 be checked by keeping the fermenting mass in close vessels, 

 the movement then slackens, and the fermentation termi- 

 nates only with difficulty and after a very long time. 



In all the experiments which I tried on fermentation, I 

 have never seen that the air was absorbed. It neither enters 

 into the product as a principle, nor into the decomposition as 

 an element ; it is expelled from the vessels with the carbonic 

 acid, which is the first result of the fermentation. 



Atmospheric air, then, is not necessary to fermentation ; 

 and if it appears useful to establish a free communication 

 between the must and the atmosphere, it is because the gaseous 

 substances which are formed in the fermentation may then 

 escape, by mixing with or dissolving in the surrounding air. 

 It follows also from this principle, that when the must is put 

 into close vessels, the carbonic acid will find obstacles to its 

 volatilisation : it will be forced to remain interposed in thie 

 liquid; it will be dissolved there in part, and, making a con- 

 tinual effort against the liquid, and each of the parts of which 



Vol. IX. ^ Tt it 



