not only the cells of alcoholic fermentation fall in, but those that produce the other kinds, notably the lactic, so that bread-making by leaven is a somewhat haphazard process; the result may be fairly good, and it may be very bad. The black sour bread of Germany and other European countries is made in this manner. The addition of hops retards decay of the yeast. Modern yeast is brewers' or beer yeast, even homemade preparations being mostly started by it; because both for beer and bread the alcoholic fermentation is desirable, and brewers, by careful study and experiment, have learned so to control the process as to obtain a yeast consisting of only one kind of organisms, Saccharomyces cerevisiæ.

When yeast is added to batter it is like the scattering of a multitude of little living cells or seeds, ready to grow with extraordinary rapidity in a medium suited to their nutrition. These cells in well-mixed batter are present at every point; and as each cell in decomposing sugar gives off tiny bubbles of carbonic acid. gas these bubbles are in every part of the dough, rendering it porous or "light." Although wheat flour contains only about one per cent of sugar, when fermentation is once started the starch is rapidly converted into sugar, and the sugar so formed into carbonic acid gas and alcohol; thus the fermentation of bread goes on at the expense of the starch of the flour. Cooked starch is acted on more readily than raw, and therefore the addition of some boiled potatoes to the sponge causes a more rapid rising.

There are two divisions of beer yeast, high (haute)

and low (basse). According to Pasteur the high buds more rapidly, floats, and is produced by fermentation at from 50° to 75° F. The low sinks, the cells are more separate, it buds only for a short time, is produced at a lower temperature (forty to fifty degrees), and is of late much used for beer. The best yeast for bread is that which floats. It is now prepared for the purpose, and when ready for use is skimmed off, drained, pressed in sacks, cut up into squares, covered with tin foil, and sold as compressed yeast. In this condition it is next best to the fresh brewers' yeast, with the advantage of small bulk and ease of transportation. If kept cool and dry it will be good for days; and if dried, not in the sun or in the oven, but in a current of warm air, it will keep indefinitely. Packages of dry yeast are composed for the most part of yeast mixed with corn or rye meal and then dried.

Yeast germs are killed by a temperature of boiling water, and freezing arrests their growth. The best temperature for fermentation of beer yeast is from 60° to 70° F.

Since the sole object of bread fermentation is the production of a porous loaf, Miss Corson's recommendation of the quick process of raising bread in two hours by the use of two squares of yeast seems to have a reasonable basis; and if the bread is, as it should be, well baked, so that the inside of the loaf has reached a temperature of boiling water, there will remain no yeasty flavor. Many loaves do not become heated to this point even when burned on the outside, consequently the yeast germs are not killed. Such slack-baked bread is not wholesome.

Yeast is not often adulterated, but its quality may vary, owing to carelessness in preparation, especially if it is homemade. There is no doubt that the compressed or Vienna yeast is the best article now at hand for producing the so-called raised bread. The color of good yeast is yellow or grayish yellow; the browner its tint the more dead germs there are. It should be only a mass of cells with no fiber or tissue. Occasionally a blue line is seen; this is due to the presence of Mucors, or molds. Such yeast makes bread which will become moldy in a very short time.

SODA, BAKING POWDERS, ETC.

The problem of making porous bread without the long process of fermentation, and the consequent loss in material which is converted into carbonic acid and alcohol, has often occupied the thought of chemists of reputation. The results have been :

First, aerated bread, made by forcing into the dough, just before baking, carbonic acid gas prepared by chemical means in another vessel.

Second, the so-called soda bread of this country, in which the carbonic acid gas is liberated from bicarbonate of soda by the use of an acid, as muriatic, tartaric, lactic (sour milk), and the acid tartrate of potassium (cream of tartar), acid phosphate of calcium, or acid lactate of calcium.

Third, baking powder bread, which is almost universally used in the United States in place of soda bread. The great advantage to the community is, that while baking powders are composed of the same

materials as those mentioned above, they are carefully mixed, so that neither acid nor alkali shall be in excess.

SODA

Soda (bicarbonate, supercarbonate, or cooking soda) is chemically a sodium hydrogen carbonate, prepared by subjecting recrystallized sal soda, or washing soda, to an atmosphere of carbonic acid gas. The only impurities likely to be found are some sulphates and chlorides remaining from the .process of manufacture of the sal soda.

CREAM OF TARTAR, ETC.

In its refined

The substances used to liberate the carbonic acid gas are practically reduced to two cream of tartar and acid phosphate of calcium. The first is prepared from imported argols, a substance used by calico printers and dyers. It is the crust which is formed on wine casks in the process of fermentation. and purified condition it is sold for bread-making. baking powder manufactory, at least, is said to use only that which has been chemically prepared. The price being from forty to eighty cents a pound, and in times of disturbance of foreign commerce even twice that, cream of tartar is the most liable to be adulterated of all the articles used in cooking.

One

Terra alba, sulphate of calcium, or, as it is commonly called, gypsum, is the substance most frequently used to make up 10 to 90 per cent of the weight of cream of tartar. It is reported that fine bone ash has been found in some samples from the Western States. In Eastern Massachusetts the most frequent

adulterant is the much cheaper acid phosphate of calcium; and since this is itself used as a substitute for cream of tartar, the effect on the bread is not as much to be feared as if gypsum were used. If it shall be proved that a certain amount of potassium salts is desirable to counteract the excessive use of salt and salted foods, the much discussed cream of tartar bread may find its place as a recognized article of diet.

Acid phosphate of calcium is prepared from bones by treating them with sulphuric acid, setting free a portion of the phosphoric acid. It is supposed to be a useful ingredient of bread, since it restores some of the phosphate said to be lost in the bran.

Acid lactate of calcium is used for a cream of tartar substitute, and in many respects it promises well. It contains the same acid as sour milk, and is prepared from starch by the action of the lactic ferment.

BAKING POWDERS

Baking powders, prepared from soda and cream of tartar chiefly, are, when put up in tin cans with the maker's name on the label, much more reliable than any other form of bread-raising preparation. Sometimes a very little bicarbonate of ammonia is added to secure a complete neutralization of the acid without leaving an excess of soda. If this amount does not exceed 1 per cent it can do no harm. As they are made in large quantities they are of a more even composition than when cooks guess at the proportions by spoonfuls. The chief adulterant used is starch or