Sift the flour, measure and resift 3 times with the baking powder and salt. Combine the spices and mix thoroughly with boiling water. Cream the butter until soft and smooth, blend in 3/4 C of the sugar, and add the beaten egg yolks. Beat until light and fluffy. Stir in spice mixture; then add flour mixture and milk alternately, beginning and ending with flour and beating until smooth after each addition. Beat egg whites, add remaining 1/4 C sugar, and continue beating until very stiff; fold into batter. Turn into two 8-inch cake pans which have been lined with thin plain paper in bottom. Bake in a moderate oven (350F) for about 25 minutes, until springy when pressed lightly with the finger tips. Cool 5 minutes before removing from pans and then turn out and cool thoroughly on cake racks. Put together with orange frosting.