That in all factories, workshops, salt blocks, saw-mills, logging or lumber camps, booms or drives, mines or other places used for mechanical, manufacturing, or other purposes within the state of Michigan, where men or women are employed, 10 hours per day shall constitute a legal day’s work; and any proprietor, stockholder, manager, clerk, foreman, or other employers of labor who shall require any person or persons in their employ to perform more than 10 hours per day, shall be compelled to pay such employes for all overtime or extra hours at the regular per diem rate, unless there be an agreement to the contrary.