Section 1. COUNTIES WITH 50,000 TO 51,000; 38,765 TO 38,775; 29,210 TO 29,630. From and after the passage of this Act in all counties of the State of Texas having a population of not less than fifty thousand (50,000) and not more than fifty-one thousand (51,000), according to the last preceding Federal Census, the salary of the county superintendent of public instruction shall be not less than Three Thousand, Three Hundred Dollars ($3,300) nor more than Three Thousand, Six Hundred Dollars ($3,600) per annum to be fixed by order of the board of education of such counties; and in counties having a population of not less than thirty-eight thousand, seven hundred and sixty-five (38,765) and not more than thirty-eight thousand, seven hundred and seventy-five (38,775), according to the last preceding Federal Census, the salary of the county superintendent of public instruction shall be Three Thousand, Three Hundred Dollars ($3,300) per annum; all counties in this State which have a population of not less than twenty-nine thousand, two hundred and ten (29,210) and not more than twenty-nine thousand, six hundred and thirty (29,630) according to the last preceding Federal Census, the salary of the county superintendent of public instruction shall be Three Thousand Dollars ($3,000) per year or Two Hundred and Fifty Dollars ($250) per month, to be paid in accordance with and in the manner as provided by general law governing the maintenance of the office of county superintendent, as provided in Article 2700, Revised Civil Statutes of Texas of 1925.