Fermentation is a Change in Vegetables by Means of some intestine Motion, the Effect whereof is, that in Distillation there arises a volatile inflammable Liquor, capable of mixing with Water, commonly called Spirits; or if the Fermentation be so managed as to produce Vinegar, thence arises in Distillation a watry, thin, acid Liquor, capable of extinguishing Fire. I have here only mentioned the Effects of Fermentation; what this intestine Motion is, or its Cause, I do not pretend to describe, because I do not know it: Its Effects are very well known to be either a vinous or an acetous Liquor, and they are producible from all Vegetables, and from Vegetables only; for all the Art yet known will never gain such Spirits either from Fossils or Animals: Putrefaction, Digestion, and Effervescence are all done by intestine Motions, but will neither produce Wine nor Vinegar; so that in this Light Fermentation is confined to Vegetables. It needs no very deep Enquiry into the History of Fermentation, to know, that in Wine (by which Name I understand all fermented Vegetable Liquor, Ale, Beer, Mead, and all artificial Wines, as well as that made from the Grape) the Spirituous Parts of the Vegetable are so volatilized and loosened, that very small Heat raises them from the other Parts of the Liquor, even many fly off upon being exposed to the Air: The viscid, oily, and glutinous Parts of Vegetables are so broke and separated, and the Spheres of their mutual Attractions so diversified, that they are no longer retained. Before Fermentation, the longer you boil the Decoction of any Vegetable, its oily and spirituous Parts are more concentrated, and little besides Water, and some essential Oyl goes away; after Fermentation the Spirit goes away, and the Water remains: This is commonly known to Brewers and Distillers. What is next observable in this Change is, that the essential Salt is thrown from the Body of the Liquor thus fermented, and adheres to the Side of the Vessel wherein the Liquor is deposited, and crystallizes into Tartar. In Vinegar this Salt is kept in the Mass of the Fluid (the Oyl being thrown off) where uniting with the aqueous and spirituous Parts, it turns sowre, and becomes Vinegar by Means of that Fermentation. After this no Tartar can be generated from it, nor any inflammable Spirit obtained; but on the contrary, a watry, poor, acid Liquor, capable of extinguishing Fire, rises first from the Still. In Wine, the volatile Salt and Oyl of the Vegetable are attenuated and reduced into one Spirit; Vinegar is the essential Salt of Wine made more acid by a new Fermentation, and intimately mixed with the watry and spirituous Parts of the same. The Spirit produced from the Distillation of Wine is a Liquor of such active Parts, and capable of effecting such Changes in animal Bodies, that it ought to be retained entirely to Medicine; but since it is too much used in Diet, it may be proper to remember it under that Head.