But let us endeavor to understand this process of fermentation. To speak in the language of chemistry, sugar is composed of certain proportions of carbon, oxygen and hydrogen. The yeast, acting on the sugar, overcomes those affinities by which these substances are held in the constitutional arrangement of sugar, and the process of decay or decomposition of the sugar takes place, which is called vinous fermentation. By this process of decay, two other forms of matter are produced, of an essentially different nature from each other and from the sugar. One of them is called carbonic acid gas or air, being formed by a chemical combination of certain proportions of carbon and oxygen. The other is known by the name of alcohol, and consists of a chemical combination of certain proportions of carbon, oxygen, and hydrogen. Carbonic acid gas is also produced by animal respiration or breathing, by the combustion of wood, coal, &c. &c. and in other ways of nature and of art: but neither in nature nor in art is there any known way by which alcohol can be produced, except by that process of the decay or destruction of sugar called vinous fermentation. The carbonic acid gas, produced in the manner I have stated, is the air which inflates or puffs up and swells out the bread, when there is sufficient gluten or other cohesive matter in the dough to prevent its escape. If the dough be permitted to stand too long in a warm place, the fermentation, having destroyed most or all of the sugar, will begin to act on the starch and mucilage, and destroy their nature, and produce vinegar; and therefore this stage of it is called the acetous fermentation: and if it still be permitted to go on, it will next commence its work of destruction on the gluten; and this is called the putrefactive fermentation, because it in many respects resembles the putrefaction of animal matter.