¶1We think it very clear that the parol evidence, so far as it related to the plaintiff’s agreement at the time of his discharge from the ship, was rightly admitted at the trial. This evidence is in no respect contradictory to the written contract. It is evidence of a new contract, made on a good consideration, and is binding on the parties.
¶2On the written contract, no action can be maintained, as it has not been performed on the part of the plaintiff. He shipped eight months after the voyage commenced, and was discharged four or five months before it terminated. The parol agreement, therefore, as to his discharge, is essentially necessary to the maintenance of the action. But if it were otherwise, the parol evidence does not contradict m any respect, the written contract. It proves a subsequent contract, and whether that is or is not *70conformable to the contract made when the plaintiff signed the shipping paper, is immaterial. As to the proof of a custom to settle lays according to the terms of the parol agreement, that was undoubtedly admissible to explain any ambiguity, if there were any, as to the principle of adjustment. That evidence, however, was offered for the purpose of explaining an ambiguity in the written contract, and is not necessary to aid the construction of the parol agreement, the proof of which is sufficient without any evidence of custom. The master’s order on the defendants was to pay to the plaintiff the net amount of his share according to his services on board the ship, agreeably to his contract specified in the shipping paper. The meaning and construction of this order are sufficiently clear. The plaintiff was to receive his share according to the terms of the shipping paper, during the time he served on board the ship, but certainly not for the whole voyage, nor for the residue of the voyage after he was discharged. He is entitled to his lay in proportion as his time of service bears to that of the whole voyage. According to the agreement of the parties, an assessor is to be appointed to compute the plaintiff’s claim, on this principle.