The State Librarian shall annually call a convention of county librarians, to assemble at such time and place as he deems most convenient, for the discussion of questions pertaining to the supervision and administration of the county free libraries, the laws relating thereto, and such other subjects affecting the welfare and interest of the county free libraries as are properly brought before it. All county librarians shall attend and take part in the proceedings of the convention. The actual and necessary expenses of the county librarians attending the convention shall be paid out of the county free library fund.