In all counties having a population of not less than twenty-two thousand, five hundred (22,500) and not more than twenty-two thousand, six hundred (22,600), according to the last preceding Federal Census or any subsequent Federal Census, the county board of school trustees shall make provisions for the traveling expenses of the county superintendent of public instruction, and shall make an allowance for such traveling expenses in the sum of Six Hundred Dollars ($600) per annum, and no more. The amount allowed herein shall be paid in twelve (12) monthly installments and in the same manner as the salary and maintenance of the office of county superintendents are now paid.