In counties having a population of not less than one hundred eighty-five thousand (185,000) nor more than two hundred fifty thousand (250,000), the boards of county commissioners of said counties, in addition to the rate of levy authorized by Kan. Stat. Ann. §§ 79-1946 and 79-1947, are hereby authorized to levy an additional tax of not to exceed six mills, to provide for salaries of officials and employees and other expenses as provided by law and to pay a portion of the principal and interest on bonds issued under the authority of Kan. Stat. Ann. § 12-1774, and amendments thereto, by cities located in the county. Said levy shall be in addition to all other expenses as provided by law.