To understand proportioning the ingredients, the nature of the ingredients when heated must be taken into account. Butter and other fats melt when heated, and behave like a liquid in the mixture. Therefore, when there is a very large amount of butter, no other wetting is necessary, as in pound cake. We may make a scale, with a thin popover mixture at one extreme, with no butter in it, and the stiff pound cake at the other, with butter the only liquid (except the flavoring). Between these two are the mixtures of medium stiffness, with both butter and liquid. This general rule may be given: As the quantity of butter is increased, the batter must increase in stiffness, and there must be either less liquid or more flour. A beaten egg looks like a liquid and behaves so during the mixing, but in the oven it stiffens. For this reason we can make a sponge cake with many eggs and no liquid in the mixing, and use no other leavening agent than the air beaten into the egg. One old-fashioned rule for sponge cake reads: Take the weight of the eggs in sugar and half their weight in flour, with the juice and rind of a lemon for ten eggs. Such a rule was adapted to the days when eggs were cheap. We should now use fewer eggs in sponge cake, and this means that water and baking powder must replace the eggs omitted. =Methods of mixing.=——(1) _For popovers, griddlecakes, muffins, and plain cake._ Sift together the dry ingredients. Beat the eggs, without separating the yolk and white, and stir the eggs and milk together. Pour the liquid gradually into the flour, first stirring, then beating. Melt the butter or other shortening, and beat it into the batter. (2) _Biscuits and shortcakes._ Sift together the dry ingredients. Cut in or chop in the butter. Add the wetting slowly. (3) _A richer, fine-grained butter cake._ Sift together the dry ingredients. Cream the butter, and beat in the sugar. Beat the whites and yolks of the eggs separately. Beat the yolks into the creamed butter and sugar. Add the flour and milk alternately; that is, a quarter or third of the flour, then a portion of the milk, and so on. First stir, then beat vigorously. Fold in the beaten whites lightly and do not beat the mixture again. (4) _Sponge cake._ If baking powder is used, sift with the flour. Beat the whites and yolks of the eggs separately. Beat the sugar into the yolks, and add the liquid and flavoring. Add the flour and beaten whites in alternate portions, dividing both into quarters or thirds. =Baking.=——This is a science and an art that requires much practice. Do not be discouraged if you do not succeed at first.