Wine 



fermentation : it goes on in the very sub- 

 stance of the sugar, which is gradually decom- 

 posed and separated into two bodies, very 

 different from each other and from the sugar 

 that produced them. One of these is alcohol 

 and the other a gas with which we are already 

 acquainted — carbonic acid gas — the same that 

 feeds the plants and causes coal to burn, but 

 which cannot be breathed by animals. The 

 alcohol remains in the liquid, which gradually 

 loses its former sweet taste, and adopts that 

 of wine. The gas, on the other hand, rises, 

 stirring up the whole with a violent motion 

 like that of boiling water, and is dispersed in 

 the atmosphere. 



You will remember that carbonic acid gas 

 is as invisible as air itself, that it has neither 

 smell nor colour, and will kill at once if 

 inhaled freely. This will show how dangerous 

 it would be to enter a vat in a state of fer- 

 mentation, or even a cellar where there is 

 not a sufficient draught to carry off the 

 formidable gas. This should only be 

 attempted while carrying before one a lighted 

 taper attached to a long stick. As long as 

 the taper burns as usual we may advance 

 boldly — there is no carbonic acid gas. But 

 if the flame turns pale, diminishes and goes 



223 



