And be it further enacted by the authority aforesaid That no person or persons whatsoever shall be obliged by vertue of any contract made att any time before the First day of December One thousand six hundred ninety three to deliver any Salt or Rock Salt unlesse the person who is to receive the same shall before or att the time for delivery of the same by such contract pay to the seller thereof such su[m]m or su[m]ms as hee shall have paid or secured to pay for the Duty for the same by vertue of this Act.