810 APPENDIX. 
We have already mentioned elsewhere, that the beer manufacturers 
of Bavaria were in possession of this secret. Chance, aided by the 
very low and suitable temperature of the climate, seemed to have been 
the accidental cause of this interesting discovery. Its practical ope- 
ration is very simple. It consists in carrying on the fermentation of 
the sweet juice at a temperature of nine or ten degrees centigrade, in 
shallow vessels with large surface, which are left without any other 
care than from contact with atmospheric air. 
By these processes, beers, ciders, and wines, acquire a great preserva- 
tive quality. They are not at all affected with the variations of the 
temperature ; and what is remarkable, they are as perfect some weeks 
after fermentation as if they were two or three years old. 
To thoroughly comprehend upon what law these good results depend, 
it is indispensable to know the phenomena which occur in the alcoholic 
and acetic fermentations. The ferments, which are the producers of 
the fermentations, are azotized substances, in condition to unite with 
oxygen, for which they possess a great affinity. They have, further- 
more, the faculty of transmitting the action with which they are 
endowed, that is to say, the fermentation, to the sweet alcoholic 
liquids with which they are placed in contact ; but the degrees of tem- 
perature necessary for these transformations are not the same for these 
two different fluids. The degree the most favorable for the conversion 
of the alcohol into acetic acid (vinegar), by means of a ferment, lies 
between twenty-five and thirty degrees of centigrade ; at nine and ten 
it loses completely this faculty, and it is no longer in action upon the 
alcohol. On the contrary, the oxidation of the ferment at this low 
temperature, does not experience any obstacle—not more than that of 
the sweet liquid to which it imparts its action, converting it into alcohol 
by means of oxidation or fermentation. 
Let us now apply this principle, deduced from the attentive observa- 
tion of facts, to the manufacture of wines, as it is practiced. As soon 
as the expressed juice of the grapes comes in contact with atmospheric 
air, its ferment combines with the oxygen, and it produces at the same 
time in the sweet liquid a like phenomenon. <A part of the carbon of 
the sugar unites with the oxygen of the air, and escapes in the state 
of carbonic acid gas. The other part is converted into alcohol. This 
