Two opposite practices prevail, in the manufacture of the same sort of wine; _some wine-makers boiling the juices before fermentation, others conducting the whole process without boiling:_ the propriety or impropriety of these practices depends upon the quality of the juices to be vinified. Extractive matter is partially coagulable by heat; boiling therefore, by causing this matter to separate and to be deposited, tends to the production of a sweet wine. The extractive matter may also be precipitated by sulphuric acid gas, (burning in the cask a brimstone match as hereafter directed,) or by sulphuric acid itself, with which the soluble leaven forms an insoluble compound. Hence where the extractive matter is in excess, and where there is danger of fermentation going on too rapidly, boiling or sulphuring will be useful both to the wine and cider-maker, in checking or preventing fermentation. The superfluous extract thrown up in the course of fermentation as yeast, or deposited as lees, will, if remixed with the liquor, have the effect of continuing the fermentation: hence the utility of racking and fining, where it is in excess; and of re-union, where it is deficient. _Artificial leaven or yeast_, which contains the extractive principle in great abundance, affords a supply to those juices which are deficient in it, and without which they will not ferment. _Natural leaven_ (i. e. _extractive matter_) is soluble in cold water, artificial leaven is not: during fermentation, therefore, the latter is always thrown off; so also is the greater part of the former, if the process be well conducted. Most of the fruits of this country abound in _malic acid_; those that possess only a moderate quantity of it, however, afford excellent wine with the addition of sugar only; still better wine may be obtained by the further addition of the acid of tartar. Where the malic acid prevails so abundantly as to make its neutralization desirable. +Dr. McCulloch+, (to whom I am indebted for much of the information contained in this chapter,) recommends the coating of the insides of the fermenting vats with a white wash of hot _caustic lime_. I have neutralized the malic acid, by putting into the cask, after the sensible fermentation has been completed, about a pound of _egg shells_ to every sixty gallons of wine. The acid of tartar increases the fermenting power of fluids: half-ripe fruits possess it in greatest abundance; hence the vivacity of champagne and green gooseberry wine. It is most conveniently used in the state of supertartrate of potash or common cream of tartar: the common rough tartar is in some respects preferable, as its admixture of yeast assists in perfecting the fermentation.