54 STAT.] 76TH CONG. , 3D SESS.- - CI. 919-NOV. 26, 19-0 (b) Whenever the President, upon report and recommendation by the Commission, shall find and declare that one or more officers or positions to which the Classification Act of 1923, as amended and extended, is applicable, may not fairly and reasonably be allocated to the professional and scientific service, the subprofessional service, the clerical, administrative, and fiscal service, the custodial service, or the clerical-mechanical service, as described in the Classification Act of 1923, as amended, he may by Executive order prescribe and define such additional classification services and grades thereof as he may deem necessary and shall describe, and fix the ranges of compensation for, the grades of such services within the limits of the Classification Act of 1923, as amended, so that they shall be comparable, as nearly as may be, with the grades in said Act, as amended, for offices or positions that are comparable as to duties, responsibilities, qualifications required, and other conditions of employment. (c) Whenever the President, upon report and recommendation by the Commission, shall find and declare that the rates of the com- pensation schedules of the Classification Act of 1923, as amended, are inadequate for any offices or positions under such Act, as amended and extended, he may by Executive order establish neces- sary schedules of differentials in the rates prescribed in such com- pensation schedules, but the differentials in the compensation of any such office or position shall not exceed 25 per centum of the minimum rate of the grade to which such office or position is allocated under such compensation schedules: Provided, That the provisions of this subsection shall be applicable only to such offices or positions having the following characteristics: Offices or positions which are located at stations that are isolated, remote, or inaccessible when compared with stations at which offices or positions of the same character are usually located, or which involve physical hardships or hazards that are excessive when com- pared with those usually involved in offices or positions of the same character, or which are located outside the States of the United States and the District of Columbia: Provided further, That nothing herein contained shall preclude the Commission from taking the factor of isolation, hardship, hazard, or foreign service into con- sideration in allocating a given class of offices or positions to a service and grade under the Classification Act of 1923, as amended, if such factor is uniformly involved in each office or position in the class, in which event no differential is authorized under this section. (d) Except as Congress may otherwise provide by law, the power granted to the President by this section shall not apply to the following: (i) Offices or positions in the Postal Service the compensation of which is fixed under an Act of Congress approved February 28, 1925 (43 Stat. 1033), as amended; (ii) Offices or positions of teachers, librarians, school-attend- ance officers, and employees of the community-center department under the Board of Education of the District of Columbia, the compensation of which is fixed under an Act of Congress approved June 4,1924 (43 Stat. 367), as amended; (iii) Offices or positions in the Metropolitan Police, in the Fire Department of the District of Columbia, and in the United States Park Police, the compensation of which is fixed under an Act of Congress approved July 1, 1930 (46 Stat. 839); (iv) Commissioned officers and enlisted personnel in the mili- tary and naval services and the Coast Guard, and commissioned officers in the Public Health Service and the Coast and Geodetic 1213 Additional classifi- cation services and grades. 42 Stat. 1488 . 5 U. . C. §H661-674; Supp. V , §§ 673, 673c. Ranges of compen- sation. Schedules of differ- entials in compensa- tion rates. Limitation. Provisos. Applicability. Offices or positions at isolated stations, etc. Isolation, etc., as factors in allocations. 42 Stat. 1488. 5 U.S.C. §§66l- 74; Supp. V , i 673:. 6 7: 3 c. Nonappilcation of President's power to designated offices or positions. 43 Stat. 1053. 7 D. C. Code 5S31- 47; Supp. V, §31-46. 20 D. C. Code, Supp. V, §§ 457a, 555a, 582 (note), 582a, 582b, 617, 618.