Soak 1 package gelatine in two-thirds cupful cold water five minutes. Dissolve 1 lb. sugar in two-thirds cupful cold water, and when it comes to boiling-point add the gelatine, and boil steadily 20 minutes. Add the grated rind and juice of one orange, and juice of one lemon. Wet tin with cold water, and pour in mixture to the depth of one inch. When firmly set, immerse mould in warm water; turn out, cut in cubes, roll in powdered sugar into which has been sifted a teaspoonful of cornstarch.