The compensation board, in addition to other powers herein granted, shall have the power to compel the attendance of witnesses to testify before it on all matters connected with the operation of this chapter and its chair or any member of said board may administer oath to such witnesses; to make all necessary rules and regulations for its guidance in conformity with the provisions of this chapter: PROVIDED, HOWEVER, That no compensation or emoluments shall be paid to any member of said board for any duties performed as a member of said compensation board.