Section 25. For section 44 of the principal Act, the following section shall be substituted, namely:

25. For section 44 of the principal Act, the following section shall be substituted, namely:— Substitution of new section for section 44. "44. (1) No adolescent who has not been granted a medical certificate certifying that he is fit for work as an adult shall be employed or permitted to be employed above ground in a mine— Working hours for adolescents not certified to be fit for work as adults. (a) for more than four-and-a-half hours in any day, and (b) between the hours of 6 P.M. and 6 A.M. (2) The period of work of all such adolescents employed in a mine shall be limited to two shifts which shall not spread over more than five hours each, and there shall be no change of shifts except once in a period of thirty days and with the previous permission in writing of the Chief Inspector.".