and the Method of making Wines . 345 
principles which may direct the agriculturist in the art 
of managing it. 
Of the Causes which have an Influence on Fermentation , 
It is well known that to establish fermentation, and 
make it follow all its periods in a regular manner, some 
conditions with which observation has made us acquaint- 
ed are necessary. A certain degree of heat, the contact 
of the air, the existence of a sweet and saccharine prin- 
ciple in the must— such are nearly the conditions that are 
requisite ; we shall endeavour to make known the effects 
produced by each of them. 
i. Influence of the Temperature of the Atmosphere on 
Fermentation . 
The 54th degree of Fahrenheit is pretty generally 
considered as the temperature most favourable to spiri- 
tous fermentation ; below that degree it is languid § 
above, it becomes too tumultuous. At a temperature too 
cold or too hot, it does not take place at all. Plutarch 
observed that cold could prevent fermentation, and that 
the fermentation of must was always proportioned to the 
temperature of the atmosphere.* Bacon recommends 
the immersion of vessels containing wine, in the sea, to 
prevent its decomposition. Boyle relates, in his Trea- 
tise on Cold, that a Frenchman, to keep his wine in the 
state of must, and preserve to it that sweetness of which 
some persons are fond, closed the cask hermetically, and 
immersed it in a well or a river. In all these cases the 
liquor was not only kept in a temperature very unfavour-* 
able to fermentation, but it was secured from the contact 
of the air, which checks, or at least moderates, fermenta- 
tion. 
An extraordinary phenomenon, but which seems con- 
* Qusest Nat. 27- 
You il x x 
