Section 1. From and after the passage of this Act, in all counties of the State of Texas which had a population of not less than twenty thousand, seven hundred and ninety (20,790) and not more than twenty thousand, eight hundred and twenty-five (20,825), according to the last preceding Federal Census, the salary of the County Superintendent of Public Instruction shall be Twenty-four Hundred Dollars ($2400) per annum, to be paid in accordance with and in the manner as provided by General Law governing the maintenance of the office of County Superintendent of Public Instruction.