As malt liquors require the addition of other substitutes, besides water, to, become perfect wines, they can only be ranked in the _second_ class of _artificial_ fermentation. These substitutes are properly called _ferments_, and merit the brewer’s closest attention. Ferments, in general, such as yeast, flowers or lees of wine, honey, the expressed juices of ripe fruits, are subjects more or less replete with elastic air, and convey the same to musts, which stand in need thereof. Boerhaave has ranged these, and several others, in different classes, according to their different powers, or rather in proportion to the quantity of air they contain for this purpose. The juice of the grape, when fermented, forms more lees than the extracts of malt. May we not, from thence, infer that, in the fruit, the elastic air is both more abundant, and contained in a greater number of stronger, though smaller, vesicles, than it is in the malt? The barley, being first saturated with water, germinated only, and then dried with a heat far exceeding that which ripened it, or that which fermentation admits of, has its air in part driven out. The expulsion of air from the worts of beers and ales is still farther effected by the long boiling they undergo. Hence the necessity of replacing the lost elastic air, in order that these extracts may become fermentable. This is effected by means of the yeast, which, consisting of a collection of small bubbles, filled with air, and ready to burst by a sufficient heat, becomes the ferment, which facilitates the change of the wort into a vinous liquor. The musts of malt generally produce two gallons of yeast from eight bushels of the grain, whereas, in the coldest fermentable weather, and for the speediest purpose, one gallon of yeast is sufficient to work this quantity of malt. Much elastic air still remains in beer, or wine from corn, after the first part of the fermentation is over; for the liquor, separated from the yeast above mentioned, is, at the time of this separation, neither flat, vapid, nor sour; but as yeast, the lees and flowers of malt liquors are of a weaker texture than those of grapes, all artificial fermentations should be carried on in the coolest and slowest manner possible: and beers, but more especially such as are brewed from high-dried, brown malts, (the heat of whose extracts approaches much nearer to that which dried the grain, than is the case in brewing pale malt) ought not to be racked from their lees, as it is frequently practised for natural wines, unless, on account of some defect, they are to be blended with fresh worts under a new fermentation.