(1) No adult employed above ground in a mine shall be required or allowed to work for more than forty-eight hours in any week or for more than nine hours in any day:
     ¹[Provided that, subject to the previous approval of the Chief Inspector, the daily maximum hours specified in this sub-section may be exceeded in order to facilitate the change of shifts.]
     (2) The periods of work of any such adult shall be so arranged that, along with his interval for rest, they shall not in any day spread over more than twelve hours, and that he shall not work for more than five hours continuously before he has had an interval for rest of at least half an hour:
     ²[Provided that the Chief Inspector may, for reasons to be recorded in writing and subject to such conditions as he may deem fit to impose, permit the spread-over to extend over a period not exceeding fourteen hours in any day.]
     ³[(3) Persons belonging to two or more shifts shall not be allowed to do work of the same kind above ground at the same time:
     Provided that, for the purposes of this sub-section, persons shall not be deemed to belong to separate shifts by reason only of the fact that they receive their intervals for rest at different times.]