Sec. 3. The salaries of the County Superintendent of Public Instruction of each county in Texas having a population of not less than twenty-two thousand, six hundred (22,600) and not more than twenty-two thousand, eight hundred (22,800), according to the last preceding Federal Census, shall from and after the passage of this Act be not less than Twenty-two Hundred Dollars ($2200) per annum and not more than Twenty-eight Hundred Dollars ($2800) per annum, and in counties having a population of not less than fourteen thousand, five hundred and fifty (14,550) and not more than fourteen thousand eight hundred (14,800), according to the last preceding Federal Census, shall from and after the passage of this Act be not less than the sum of Twenty-two Hundred Dollars ($2200) and not more than Twenty-eight Hundred Dollars ($2800) per annum, to be fixed by the County Board of Education in each county.