Patras .. 15 „ Madeira 2.5 „ Champagne .. .. 7 „ Sherry .. .. 2 The agreeable, vinous odour of grape-wines is imparted by a minute proportion of an ethereal substance termed osnanthic ether. This substance, when separated from the wine, is a mobile, volatile liquid, possessing an exceedingly sharp, unpleasant taste, hnd so powerful an odour as to be almost intoxicating. It does not exist naturally in the grape, hut is formed during fermentation, and it appears to increase in quantity as the wine grows oldi,r. The faintest trace is sufficient to impart bouquet, since few wines contain more than 7,,,4,57,- part of it by volume. This ether is present in all wines; there are other ethers, however, which possess less fragrance, and which are different in different varieties of wines, giving to each the peculiar bouquet hy which it is characterized ; these are present in even smaller quantities than the oenanthic ether. The formation of these is due to the action of the aoids in the wine upon the alcohol, as shown in the following equation, in which ethylio acetate is formed by the union of acetic acid and alcohol :— Acetic acid. Alcohol. Ethylic acetate. Water.
C211,0t0 C21-1,10 C2112 HI Hf = -I- H20.
Some wines acquire their aroma partly during fermentation and partly after storage.
The following table gives the average proportional quantities of some of the chief constituents of wine per litre. The figures are obtained from analyses of French, Swiss, and German wines :— Red wines are richer in phosphates than white wines because the former remain for a longer time in contact with the seeds and skins of tho grape, which are extremely rich in phosphates. Tartaric acid exists in tbe natural juice of the grape as bitartrate of potash or cream of tartar.
• After fermentation, and when the wine is left at rest, this salt separates out, and is deposited in a thick crust upon the sides of the casks or bottles. The presence of this acid in wine tends to diminish the exciting or intoxicating effects of alcohol ; hence, as the wine gets older, it gradually becomes less acid, and stronger in proportion. Every year, therefore, added to the age of a good wine increases its strength and value.
The principal effect of the presence of tannic acid or tannin is to aid in preserving wine, and to moderate the action of the alcohol. Wines containing much taunin produce intoxication much more slowly than those which contain but little. The wines of Bordeaux contain a large proportion of the astringent principle, and to this is probably due the fact that they are much less intoxicating than other varieties which are not more alcoholic.
New wine contains more than its own volume of dissolved carbonic acid gas, formed during fer mentation. This quantity, however, diminishes during storing, by diffusion through gie pores of the casks, its place being taken by atmospheric air, which assists in maturing the wine. When bottled, it does not usually contain more than one-fourth of this quantity. When not in excess, its presence is believed to moderate the intoxicating influence of the wine, acting more or less as a cor rective. It produces a. gentle, stimulating effect upon the stomach, and greatly assists digestion.
Wines, however, like champagne and sparkling hock, which contain much carbonic acid, are doubtless rendered more " heady " by its presence.
The remaining acids, acetic, mall°, pectic, &c., are seldom abundant in good wines, and have but little influence upou them beyond neutralizing, to some extent, the action of the alcohol.
The general physiological effects of wine are well known. The first effect, when taken into the stomach, is to stimulate the action of that organ, producing in it, at the same time, a geutle aud agreeable warmth. After a short time, the spirit penetrates into the blood, the movements of the heart and lungs are rapidly accelerated, the heat of the entire system is increased, and the circula tion of the blood powerfully excited. If the quantity imbibed is too great, the pressure of blood in the brain becomes intense, and intoxication rapidly ensues.
Vinee cannot be grown in any elimate. The proper development of perfume and of sufficient sugar in the gmpe requires a warm and constant sun, such as is to be had only in the warmer climates. The cultivation of the vine is most successfully carried on in the countries lying between the 35th and the 50th degree of latitude, and it is in these that the most celebrated vine-growing districts are situate. Colder climates produce wines poor in alcohol, though sometimes of very agreeable perfume ; they are difficult to keep, and turn sour with remarkable rapidity, since they do not contain enough alcohol to preserve them.
The nature of the soil in which vines are grown exerts considerable influence upon the quality of the gmpe. Vines will grow everywhere, and in a fertile soil will flourish exceedingly ; but experience has shown that the value of the wine is rarely proportional to the luxuriance and strength of the vine from which the grapes were obtained. Hard, clayey soils are not favourable to the growth of grapes ; neither are clamp soils, of any nature whatever. They yield vigorous and beautiful vegetation, but wine obtained from them is invariably watery and wanting in bouquet. A calcareous soil is, as a rule, highly favourable ; the culture of the grape in light, dry soils is more simple than in any other, and they yield a wine which is spirituous and of a flne bouquet and flavour. The best possible soil is that which is at the same time light and flinty. Volcanic earths yield very delicious wines, as proved by those of Tokay and the finest Italian wines. To sum up, the vine may be cultivated advantageously in a great variety of soils, provided they be light, dry, finely divided, and such as will readily receive and filter water. Heavy, moist, or clayey earths must be avoided in laying out a vineyard, and the first consideration should always be lightness and porosity.