delivered the opinion of the court.

This action was instituted against the defendant as the acceptor of a bill of exchange. Upon the trial, and after the production of the bill declared on, the acceptance of which was not denied by the defendant, the defendant offered to read in evidence a deposition which went to show that the acceptance was given to the plaintiff upon a condition that the drawer finished a job of work which he had undertaken for the acceptor. The probable object of the introduction of the deposition was to take the first step in attacking the consideration for which the acceptance was given ; and a failure of consideration may be proved by parol. But in laying this foundation, it was necessary to reach back to the prime contract in writing, which was explicit in its terms, and free from ambiguity, and could not, therefore, by the long established rules of evidence, be thus approached. The contract to pay as acceptor was in writing, and therefore could not be changed by parol; the deposition *248went to show that there was not a positive agreement to pay as acceptor, and therefore, being parol testimony, was not admissible. 14 Mass. 154 ; 1 Cow. 249 ; 7 Mass. 518. Moreover, in respect to this case, the deposition does not sufficiently identify the bill sued upon in the action with the one respecting which the defendant speaks.

Judgment affirmed.