Combine egg whites, sugar, and orange and lemon juice in top of double boiler, beating with rotary egg beater until thoroughly mixed. Place over rapidly boiling water, beat constantly with rotary egg beater, and cook 7 minutes, or until frosting will stand in peaks. Remove from boiling water, add orange rind and beat until thick enough to spread. Makes enough frosting to cover tops and sides of two 9" layers, or the top of one 10" layer and sides of three 10" layers.