No examination for inspectors of coal-mines shall exceed in duration the period of forty days in the bituminous districts, and the period of twenty days in the anthracite districts; and no examination of mine foremen, assistant mine foremen, and fire bosses in the bituminous districts, and mine foremen and assistant mine foremen in the anthracite districts, shall exceed in duration the period of ten days: Provided further, That no indebtedness shall be incurred until the authority for the same shall have been granted by the Department of Mines.
52 P.S. § 733