When the meal is thus prepared and brought home, whether in a barrel or sack, the next thing to be attended to, is, that it be placed and kept in a perfectly clean, and sweet, and well ventilated meal room. It should on no consideration be put into a closet, or pantry, or store-room, which is seldom aired, and more rarely cleansed; and into which all manner of rubbish is thrown; or even where other kinds of provisions are kept. If the meal be put into a pantry or store-room which is confined and dirty, and into which old boots and shoes, and old clothes and pieces of carpet, and other things of this kind, are thrown—or where portions of vegetable or animal substance, whether cooked or uncooked, are habitually or even occasionally put and permitted to remain, it must be expected, as a matter of course, of necessity, that the quality of the meal will be considerably deteriorated by the impurities with which the air of the place will be loaded, and which will be continually generated there. People generally have but a sorry idea of what constitutes true cleanliness; but they may be assured that they cannot be too deeply impressed with the importance of keeping their meal room as clean and sweet and well aired as possible. FERMENTATION. Chemical composition of flour. Yeast—modes of preparing it. Substitutes for it. Fermentation, and its products. Vinous, acetous and putrefactive fermentation. Having procured good wheat, cleansed it thoroughly, and got it properly ground, and placed in the meal room, the next step is to take a portion of the meal and manufacture it into good bread. But in order that this may be done in the most certain and perfect manner, it is important that the properties of the meal and the principles concerned in bread-making should be well understood.