The necessary expenses of the board of sinking fund commissioners incurred in the performing of any of their duties imposed upon them by this act shall be a proper charge against said county to be paid from the general fund. The chairman of the board of supervisors and the chairman of the finance committee shall receive as compensation the sum of 3 dollars per day for each and every day they shall actually attend any regular or special meeting of said board of sinking fund commissioners, and they shall also receive their traveling expenses at the rate of 10 cents a mile 1 way figuring over the usual traveled route from their residence to the place of meetings of said board.