Potato Flour Sponge Cake

Separate the whites and yolks of nine eggs. Beat the whites of seven eggs very stiff. To the well-beaten yolks of nine eggs and the whites of two, add one and three-quarter cups of sugar and juice and rind of one lemon.

Beat thoroughly, add one scant cup of potato flour, and beat again.

Now fold in the beaten whites very carefully, and bake slowly in a moderate oven.

Bake forty to fifty minutes.