From and after the passage of this Act that all County Superintendents of Public Instruction in all counties having a population of not less than fifteen thousand seven hundred twenty-five (15,725) and not more than fifteen thousand seven hundred seventy-five (15,775) according to the last preceding Federal Census shall be and are allowed an additional Five Hundred ($500.00) Dollars per year for traveling expenses.
Tex. Rev. Civ. Stat. Ann. art. 2700d-21