MANUAL OF NATURE STUDY. 
69 
a warm place, temperature of a summer day, twen¬ 
ty-four hours, and watch it “work,” fermentation. 
The effervescence which you see is caused by 
the escape of carbon dioxide gas formed therein. 
The alcohol is formed at same time, but does not 
escape so readily as the gas unless warmed to a 
much higher temperature, as in baking light bread. 
In secondary fermentation the alcohol escapes, 
thus leaving acetous acid or vinegar. In the first, 
or primary fermentation, the sugar in the juice is 
changed to alcohol; in the second fermentation the 
alcohol is changed to vinegar. 
Alcohol does not exist in the fruit, or sugar, 
neither does vinegar exist in the alcohol. A fossil 
made of limestone preserves the form of 
a once living animal or plant, but the limestone 
did not exist in the living tissues of the animal or 
plant; no more does alcohol exist in living corn, 
or grape, or apple. 
Fresh oysters are wholesome food, but fossil 
oysters would lie rather heavy on the stomach. 
Fresh corn is an excellent food, but, when 
changed by fermentation into whiskey, it is poison¬ 
ous to the system. 
To make this illustration vivid, the teacher 
should show some fossil plants or animals, oysters, 
if possible, so that children may see that nature 
makes a complete change in quality and properties. 
