If we recollect that we can scarcely make wine, which will preserve itself, of grapes produced in England, we shall be induced to think, that the reason of this defect is the want of the high degrees of heat. Our sun seldom raises the thermometer to 100 degrees, and that but for a short continuance. Our medium heat is far inferior to 92, and hence we see, at several distant terms in summer, new germinated grapes, but seldom any perfectly ripe. These observations, the use of which, in brewing, we will endeavour to apply, likewise point out to us, what part of our plantations are fit to produce this fruit, and to what degree of perfection.
A research made for each constituent part forming grapes, as well as the proportion they bear to one another, at first sight, appears to be an eligible method to discover the nature of wines; but in every vegetable their parts are mixed and interwoven, and every degree of heat, acting on them, finds these so blended, as to render their division too imperfect for such enquiry to be made with sufficient accuracy, to deduce therefrom the rules of an art. In the producing, ripening, and fermenting the juice of the grapes, as well as in forming beers and ales, the element of fire so superlatively influences and governs every progressive act, as to occasion some remarkable difference in their appearance: from, hence, then, we may expect the information we want, and be enabled to discover the laws by which Nature forms her wines.
When the constituent parts of a subject are to be estimated by heat alone, the number of degrees comprehended between the first heat which formed it, and the last which brought it to a perfect state, must express the whole of its constituent parts. Complete finished substances, must have been benefited by the whole latitude of degrees applicable thereto; and in proportion as part of the whole latitude is wanting, will their nature be different, and themselves less perfect.
This variety is remarkable in the fruit we are now treating of. A country endued with the lowest germinating, and with the highest maturating degrees of heat for grapes, would produce them in the utmost perfection; that is, they would possess all the several properties they could obtain from this circumstance; consequently such are capable of forming wines that would preserve themselves a very long time, and would also become spontaneously fine. From the several heats we have observed that this fruit is capable of enduring, it is reasonable to believe the greatest number of degrees of heat employed to form all their constituent parts, must be where, during the whole space of vegetation, the heat in the shade varies from 60 to 106 degrees, and constitutes a difference of 46 degrees. So great a latitude, ordered by nature, most certainly denotes the general utility of the plant.
The climate of the southern part of France approaches nearest to this; but Spanish wines are richer; their grapes are formed by a warmer sun; their vernal and maturating heats exceed those of France; but, at the same time, their wines are more stubborn, and, to be made fine, require the help of precipitation. This variety increases according to the heat of climates: thus we see wines which come from the coast of Africa, whose richness and stubbornness are beyond the reach of any menstruum employed to fine them. Let us endeavour to reduce this apparent inconstancy to rule, in order to assist our art.—If the lowest heat which forms the grape, in the southern parts of France, be 60 degrees, and if 88 degrees, in the shade, be the mean of their maturating heat, the difference between 60 and 88, or 28 degrees, is the number which includes the constituent parts of grapes in this country, as these degrees imply the whole space of their progress. If like juices were to be imitated by art, as in our hot-houses, it is clear half the number of the degrees of heat which form the whole of the constituent parts, or 14, deducted from 74, the mean heat of their whole vegetation, would give 60, for the first heat to be employed, and this to be raised, for maturation, to 88, the greatest heat, nature in this case, permits, or 14 degrees to be added to the same whole mean. To liken the wines of Spain, where the autumnal and vernal heats are greater than in France, the heat forming the first juices must be more, as also the maturating heats; but with such practice, the number of constituent degrees would be found to be fewer, and spontaneous brightness could no more be expected, than it is found, in their wines.
A strict enquiry after the heats first and last applied to grapes, is of such consequence to ascertain the principles by which malt liquor should be formed, that, though grapes produced in England scarcely make wines which can maintain themselves sound, yet, as the rule is universal, even from them we shall be able to establish not only its certainty, but also the application of the number of the degrees found between the heats which germinate the fruit, and those which ripen them.
| From twelve years observation, we have found the mean heat in the shade, from the 1st of June, to the 15th, when grapes with us first bud forth, to be | Deg. 57.60 |
| Our greatest heat, under like circumstances, from the 15th to the 31st of July, to be | 61.10 |
| —— | |
| Their difference, | 3.50 |
| —— | |
| Their medium, | 59.35 |
| —— |
If, from their medium, 59.35, we subtract 1.75, half their difference, or half their constituent parts, we must have left 57.60 for the germinating heat; and if to their medium, 59.35, we add 1.75, half the number of their constituent parts, we shall have 61.10, the highest mean heat, in the shade, at the time the richest juices of our grapes are formed. It is true, in July, nor even in the following months, when the heat continues nearly alike, our grapes are not ripe, nor gathered; the properties raised by our greatest sunshine, as yet have not reached the fruit, and though the mean heat of the air in September and October is less, yet it is sufficient to place in the grapes the juices raised by the preceding hot sun, which concentrate and grow richer, by remaining on the plant, though, for want of a sufficient heat, they do not reach that perfection obtained in warmer climates.
The want of grapes in many parts both of America and Africa, and the reason we gave for this, (See page 55,) warrants the truth of the division we have just now made, between the germinating and maturating heats; and if the effects caused by a hot sun do not immediately benefit the fruit, by a parity of reason, after the grapes are gathered, the plant must possess, (and surely for some longer space, by a continued heat, equal, and often superior, to the vernal sun,) juices which Nature is too frugal not usefully to apply; these juices, we apprehend, assist in forming the embryo of the leaves which are fully to expand the ensuing year, and serve, by their oleaginous quality, to preserve these and the whole plant during the cold of the winter; which cold, at the same time that it contracts the pores of the vine, condenses and thickens these richer juices, from whence few, if any of them, are lost or expended by perspiration. The heat of the following spring renews their activity, when blending with those this season attracts, the leaves open, the flowers appear, and the fruit forms. Thus far we conceive the act of germination extends, provided for and assisted both by the autumnal and vernal heats, and which, in point of power, are nearly equal and uniform.
The heat of the sun, during summer months, and if to this we add the more constant heat at the roots of the vine, retained there by the density of the earth; these (though superior to the germinating heat) produce a like uniformity for maturating the fruit: thus nature, in order to implant in wines an original even taste, and to facilitate the fermentable act, amidst the great variety that appears to us in the heat of the air, seems, upon the whole, to act by steady and equal motions; or rather, perhaps, this is the best manner by which we can reduce to rule; the inconstancy of the atmosphere.