Until the election and qualification of the first inspector of mines to be elected as provided by this act, the inspector of mines and the deputy inspectors heretofore appointed by any board of supervisors shall continue to serve until their terms of office have expired, and such board of supervisors where there are iron or copper mines situated and working is hereby authorized and directed to appoint their successors and to remove the same or any one thereof whenever in its judgment the best interests of owners and employes may so require, and to fill vacancies arising from any other cause than removal, but no such inspectors of mines or deputy inspectors appointed by or serving under any appointment of any board of supervisors shall hold office beyond the first day of January succeeding the election of the first inspectors of mines to be elected as provided by this act. Such inspectors of mines and deputy inspectors heretofore appointed or to be appointed by any board of supervisors, shall perform all of the duties of inspector of mines and deputy inspectors of mines until the election and qualification of the first inspectors of mines to be elected as herein provided.