7. The native spirits of vegetables, says Boerhaave, are separated by heats between 94 degrees, and 212. To obtain the whole of these, the fire must be gradually increased; for a superior heat dissipates the spirits raised by an inferior one. Such parts as might be obtained by 100 degrees, are lost if the heat applied be much greater. It is true, the parts of vegetables immersed in water, cannot so easily be dissipated as if they were in open air, yet, by the rarefaction of the liquid, a proportional evaporation, however small, must ensue, or the oils raised by a greater heat may so effectually envelope the finer ones, as to make them hardly perceptible either to our smell or taste. Thus, though heated water is able to extract all the virtues residing in the vegetables, the different application of the fire will alter not only their proportions, but their properties also, when we consider that pure spirit of wine boils at so low a heat as 175 degrees. If the above principles be true, that surely must be the cleanest spirit which is brought over in the slowest and coolest manner; and it is more than probable, if the rules here laid down be put in practice, the grain of England will be found to yield spirits that may vie with the brandies of France, be more pure than those of the Indies, and excel those of Holland. 8. The vinegar maker is equally concerned with the distiller in the brewing process. Vinegar is produced in the last stage of fermentation, when a gross, tartareous, unctous matter, consisting of the coarser oils extracted either from the grain or the grapes, generally falls to the bottom of the liquor, and no longer prevents its acidity, or affects its flavor. Though the best vinegar proceeds either from the strongest wines or beers, this strength consists in the quantity of fermentable principles, and not in that of mere oleaginous parts. By properly adapting the extracting waters, this hurtful impediment may be removed, and the vinegar from malt liquors become as neat and as strong as that which is made from wine. 9. As the acid taste of vinegar is the effect of a continued fermentation, many people have thought it immaterial how speedily the first parts of the operation were carried on. But violent fermentations not only dissipate some of the fine oils, which should be retained in the vinegar, but also cause the must to tend towards putrefaction. Boerhaave, after he has directed a frequent transvasion of the liquor, observes that, whenever the weather or the workhouse is very hot, it is often necessary to fill the half emptied vessels every twelve hours, not only to procure a supply of acids from the air, but also to cool the wine, and check the too violent fermentation, which arising in the half full casks, might dissipate the volatile spirits, before they are properly secured and entangled by the acid. Hence the liquor might be sour indeed, but at the same time flat, and would never become a sharp and strong vinegar.