A term applied by chemists to all liquids that have become vinous by fermentation; but it is popularly considered as confined to saccharine vegetable substances that have been converted into a vinous liquid. It seems to be a necessary condition, that sugar must be present in a vegetable, to enable it to ferment and become vinous; but this, according to late discoveries, will not exclude starch, gum, and other similar products, which are capable of being converted into saccharine matter. Lavoisier stated that pure sugar alone would not ferment, but that some extractive matter, or yeast, must be added to enable it to undergo the vinous fermentation; and he considered that the effects of this fermentation consisted in separating the sugar, which is an oxide, into parts; in oxygenating the one, at the expense of the other, to form carbonic acid; in disoxygenating the other in favour of the first, to form a combustible substance termed alcohol; so that, were it possible to combine these two substances, the alcohol and the carbonic acid might reproduce sugar. It is necessary to remark, that the hydrogen and carbonic do not exist in the state of oil in alcohol, being combined with a portion of oxygen, which renders them miscible with water.

These three principles, therefore, the oxygen, the hydrogen, and the car-oonic, are here in a kind of equilibrum; and, in fact, by causing them to pass through a red-hot tube of glass or porcelain, we may recombine them, two and two together, and the product will be water, hydrogen, carbonic acid, and carbon.

In all wines may be distinguished an acid, alcohol, tartar, an extractive matter, aroma or odour, and a colourless principle, - the whole being diluted or dissolved in a smaller or larger proportion of water. An acid exists in all wines, but all are not acid in the same degree. Of some wines a natural acidity is the principal characteristic; those produced from grapes not perfectly ripe, or that grow in moist climates, are of this kind; whilst such as are the product of the fermentation of grapes that have attained complete maturity and sweetness, contain but a very small quantity of acid. The proportion of acid appears, therefore, to be in the inverse ratio of the saccharine principle, and consequently of the alcohol, which is produced by the decomposition of the sugar. Alcohol forms the true characteristic of wine. It is the product of the decomposition of sugar; and its quantity is always proportionate to that of the sugar that has been decomposed. Alcohol abounds more in some wines than it does in others; those of hot climates contain a large quantity of it; whilst those of cold climates contain scarcely any.

Ripe and sweet grapes produce it in abundance; but the wines made of grapes that are unripe, watery, and sour, yield very little.

The following is Mr. Brande's valuable table of the quantity of alcohol in different kinds of wine and spirituous liquors:-

Tartar exists in verjuice, as also in must; it contributes to facilitate the formation of alcohol. When left at rest in casks, it deposits itself upon the sides, forming a crust more or less thick, with crystals of irregular forms. Some time before the vintage, when the casks are to be got ready for receiving the new wine, they are staved, and the tartar detached from them, in order to be employed in the different uses of commerce. This salt has little solubility in cold water, but considerably more in boiling water. It scarcely dissolves at all in the mouth, and it resists the pressure of the teeth. The extractive principle abounds in must, when it appears to be dissolved by the aid of the sugar; but when the saccharine principle is decomposed by means of fermentation, the quantity of extractive matter sensibly diminishes, a part of it deposits itself in a fibrous form, and this deposit, which principally constitutes the lees, is the more considerable in proportion as the fermentation is more gentle, and the alcohol more abundant. This deposit is always mixed with a considerable quantity of tartar. There always exists in wine, a proportion of extractive matter in a state of solution, which may be separated from it by means of evaporation.

It abounds more in new wines than in old ones; and the older the wine grows, the more completely is it freed from the extractive principle All natural wines have an odour more or less agreeable to the smell. Some of them owe their reputation in a great measure to the perfume which they exhale. This is the case with Burgundy. This perfume is lost by too violent a fermentation, and becomes stronger by age. It seldom exists in very spirituous wines, either because it is concealed by the strong smell of the alcohol, or because it has been destroyed or dissipated by the violent fermentation that was requisite to develop the spirit. The colouring principle of wine belongs to the skin of the grape , for when the must is suffered to ferment without it, the wine is white. This colouring principle does not dissolve till the alcohol is developed; it is only ther that the wine acquires its colour, which is deeper in proportion to the violence of the fermentation. If we expose bottles filled with wine to the rays of the sun, a few days are sufficient to precipitate the colouring principle in large pellicles; the wine losing neither its perfume nor its strength.

A very great number of vegetable" substances may be made to afford wine, as grapes, currants, mulberries, elders, cherries, apples, pulse, beans, peas, turnips, radishes, and even grass itself. Hence, under the class of wines, or vinous liquors, come not only wines, absolutely so called, but also ale, cyder, etc. The term wine is however in a more particular manner appropriated to the liquor drawn from the fruit of the vine. The process of making wine is as follows: - When the grapes are ripe, and the saccharine principle is developed, they are then pressed, and the juice which flows out is received in vessels of a proper capacity, in which the fermentation appears, and proceeds in the following manner. At the end of several days, and frequently after a few hours, and according to the heat of the atmosphere, the nature of the grapes, the quantity of the liquid, and temperature of the place in which the operation is performed, a movement is produced in the liquor, which continually increases; the volume of the fluid increases; it becomes turbid and oily; carbonic acid is disengaged, which fills all the unoccupied part of the vessel; and the temperature rises to inconveniences than that in which the first fermentation has been too quickly suppressed; for every fermentable liquor is, from its nature, in a continual intestine motion, more or less strong according to circumstances, from the first instant of she spirituous fermentation, till it is completely purified; hence, from the time of the completion of the spirituous fermentation, or even before, the wine begins to undergo the acid, or acetous fermentation.