Fermentation, says Liebig, is not only the simplest and best, but likewise the most economical way of making light and porous bread. YEAST is a true fungous plant, which has the power of establishing fermentation and changing starch into sugar, and the escaping gas makes the loaf light and spongy. Hops prevent too great fermentation and impart an agreeable flavor. BREWERS’ YEAST is largely used when obtainable, and there are many domestic modes of preparing yeast from potatoes, flour, etc. DRIED YEAST.—But as all these fresh yeasts are liable to spoil and affect the bread unpleasantly, there is an extensive demand for a yeast which shall possess the same properties and which may be kept a long time. Hence, the various brands of yeast cakes sold by the grocer. They are made usually by adding corn meal to the yeast and carefully drying the cakes in the sun. It is singular that a fall or sudden jar may injure yeast cakes and deprive them largely of their qualities. CREAM OF TARTAR, BI-CARBONATE OF SODA, BI-CARBONATE OF POTASH (SALERATUS), are all used in bread making, and are to be had in all sorts of packages of the grocer. Cream of tartar is tartrate of potash, and is made from the argols found incrusted upon the inside of wine barrels. It should be white, and not yellowish in tint. The effect of these chemicals in raising bread is due chiefly to the liberation of the carbonic acid gas they contain when mixed with water, incorporated with the dough and put in the oven, and the great requisite is that they should be pure and unadulterated. BAKING POWDERS are much used for making light and palatable domestic biscuits, etc. They are convenient, and generally lessen the quantity of shortening required. They are made chiefly of tartaric acid and bi-carbonate of soda, and should be neutral to the taste, and without effervescence if either an acid or alkali is added. One popular variety, called “Phosphatic Baking Powder,” consists of acid phosphate of lime instead of cream of tartar, with soda. Biscuits, Crackers, etc. The word biscuit means twice baked, and is a survival from the ancient mode of cooking the cakes which is now no longer in use. Plain biscuits are said to be more nutritious than bread in the proportion of five to three, and are most digestible when light and well browned in baking, so as to turn much of the starch into dextrine. Sea biscuit or ship bread is made simply of flour and water baked at a high heat. In the large cracker bakeries the dough is mixed, rolled and cut by machinery and the cakes travel on through patent ovens until baked, when they drop out into baskets. Those made by hand are, however, considered best.