The board of supervisors in each county where an inspector of mines is so elected or appointed shall fix the compensation of such inspector and his deputy or deputies, and provide for the payment of the same: Provided, That the compensation of the inspector of mines shall not be less than $15.00 per day, and that of the deputy inspectors shall not be less than $10.00 per day for each day actually employed in the performance of their official duties: Provided further, That the compensation of inspectors and deputy inspectors shall not be paid more than 5 days in any week.