Section 3. The payments herein provided for shall be made by the State Treasurer upon warrants drawn by the Auditor General; and there is hereby appropriated the sum of three thousand one hundred dollars ($3,100), or as much thereof as may be necessary, for payment of the amount accrued to June first, one thousand nine hundred and seventeen; thereafter said payments to be made out of any unused moneys hereafter appropriated for the salary of the head or chief of any department whose office may become vacant.