Divide the difference between the per cent. of the first, and the required per cent. by the difference between the per cent. of the second and the required per cent.

Having a wine, etc., of 18 per cent., and another of 8 per cent., how much of the second is required for every gallon of the first to produce one of 12 per cent.?

Or one and one-half gallons of the second for every gallon of the first.

Or, suppose we have a wine of 15 per cent., how much brandy of 50 per cent. must be used for every gallon of the first to produce a wine of 20 per cent.?

Or one-sixth of a gallon of the brandy must be used for each gallon of the wine.

PLASTERING.

It is a Common Practice in Spain and in the southern part of France to plaster the wines, by adding more or less gypsum, or plaster of Paris. It is either thrown upon the grapes before or after crushing, or is added to the must. Gypsum is known to chemists, when pure, as calcium sulphate (sulphate of lime), but contains a certain amount of water of crystallization, and is generally found associated with other substances, such as rock salt, and calcium carbonate, or limestone. It is the commonest impurity found in spring water, and gives water its permanent hardness. Much has been written for and against the practice of plastering, and both sides of the question have strong advocates.

Objects.—There are many different reasons given for the practice, some of which are fanciful. It is claimed that it retards fermentation, and that red wines under its effects develop more color, because the marc can be left longer in the fermenting vat; that the froth of plastered wine is livelier and sooner disappears, which pleases the merchants; and that it has a preservative effect upon the wine. It is claimed by some that it renders the wine dryer and harsher, as it does, if used to excess, and by others, that it unites with a portion of the water of the juice, and renders the remaining juice richer in sugar. Again, it is added to neutralize a portion of the acid contained in the must.