Beginning back in the flour mill, the grain is ground into powder, the coarser parts of which are sifted out as bran, while the finer constitute our flour. Once in the baker's hands, the flour is mixed with water and yeast, or something which will produce the same effect. When this paste or dough, containing yeast, is set in a warm place the yeast begins' to work, as we say, and the dough to in other words, the yeast causes a change known as alcoholic fermentation to set in, one of the principal results of which is the production of carbon dioxid gas. If the dough was well mixed, this gas appears all through it, and, expanding, leavens or raises it. After the yeast has worked sufficiently the dough is shut up in a hot oven. Here the heat kills the yeast and prevents further alcoholic fermentation, causes the gas to expand and stretch open the little pockets which it forms between the particles of dough, and changes some of the water present into steam, thus raising the loaf still more. Further, the heat 'hardens and darkens the outer layers into what we call the crust. The sum of these changes in the oven we call baking. When they have been continued long enough our bread is done, ready to cool and eat.