Sec. 7. COUNTIES OF 18,000 TO 18,500. In all counties having a population of not less than eighteen thousand (18,000) and not more than eighteen thousand, five hundred (18,500), according to the last preceding Federal Census, the county board of education shall, in addition to the salaries and expenses fixed by law, allow not to exceed the sum of Three Hundred Dollars ($300) per annum for the actual traveling expenses of such county superintendents made in the performance of their duties as county superintendents and to be paid out of the State and county available school fund of such counties on order of the county board of education of such counties on the verified account of such county superintendents.