The salaries of each member of the board of commissioners in the several counties of this Commonwealth shall be as follows:

In counties of the eighth class, one thousand dollars.

In counties having a population of twenty thousand and over, and less than fifty thousand inhabitants, one thousand dollars; and, where such county commissioners are also directors of the poor, then eighteen hundred dollars.

In counties having a population of fifty thousand and over, and less than seventy-five thousand inhabitants, fifteen hundred dollars; and, where such county commissioners are also directors of the poor, then twenty-two hundred dollars.

In counties having a population of seventy-five thousand and over, and less than one hundred thousand inhabitants, two thousand dollars; and, where such county commissioners are also directors of the poor, then twenty-six hundred dollars.

In counties having a population of one hundred thousand and over, and less than one hundred and fifty thousand inhabitants, twenty-five hundred dollars; and, where such county commissioners are also directors of the poor, then three thousand dollars.

In counties over one hundred and fifty thousand inhabitants the salary shall be as now provided by law.