. . . "veyed, subject to any Mortgage, Wadset, Bond, or other Debt, or to any gross or entire Sum of Money, to be afterwards paid by the Purchaser, such Sum of Money or Debt shall be deemed the Purchase or Consideration Money, or Part of the Purchase or Consideration Money, as the Case may be, in respect whereof the said ad valorem Duty is to be paid.And;to prevent Doubts respecting what shall be deemed" . .