If there is any question as to the quality of yeast, it is always best to test it before use by adding a little flour to a small quantity and setting it in a warm place. If it begins to ferment in the course of fifteen or twenty minutes, it is good. STARTING THE BREAD.--Having secured good yeast, it is necessary in some way to diffuse it through the bread material so that it will set up an active fermentation, which, by the evolution of gas, will render the whole mass light and porous. As fermentation is more sure, more rapid, and requires less yeast to start it when set in action in a thin mixture than when introduced into stiff dough, the more common method of starting fermented bread is by "setting a sponge;" viz., preparing a batter of flour and liquid, to which potato is sometimes added, and into which the yeast is introduced. Some cooks, in making the batter, use the whole amount of liquid needed for the bread, and as the sponge rises, add flour in small quantities, beating it back, and allowing it to rise a second, third, or even fourth time, until sufficient flour has been added to knead; others use only half the liquid in preparing the sponge, and when it has well risen, prepare a second one by adding the remainder of the liquid and fresh flour, in which case the fermented batter acts as a double portion of yeast and raises the second sponge very quickly. The requisite amount of flour is then added, the dough kneaded, and the whole allowed to rise a third time in the loaf. Other cooks dispense altogether with the sponge, adding to the liquid at first the requisite amount of flour, kneading it thoroughly and allowing it to rise once in mass and again after molding into loaves. As to the superiority of one method over another, much depends upon their adaptability to the time and convenience of the user; light bread can be produced by either method. Less yeast but more time will be required when the bread is started with a sponge. The end to be attained by all is a complete and equal diffusion of gas bubbles generated during fermentation throughout the whole mass of dough. The preferable method of combining the materials needed for the batter is by first mingling the yeast with the water or milk. If condensed or dry yeast is used, previously dissolve it well in a half cupful or less of lukewarm water. Stir the flour slowly into the liquid mixture and beat it _very thoroughly_ so that the yeast shall be evenly distributed throughout the whole.