One objection is stated in the affidavit of defence, which is a sufficient reason why judgment should be refused. The plaintiffs sue on this as a promissory note. Now to constitute a promissory note, the instrument on its face must be for the payment of a sum certain, not susceptible of contingent or indefinite additions, nor subject to indefinite w contingent deductions. In this instance, the “ current rate of exchange to be added,” is clearly indefinite. See 2 Stark. 375; 4 Ba. & Ad. 619; 4 B. Moore 471.
Rule discharged.