That a receipt maybe explained by parol evidence is a principle too familiar to require authorities for its support. The bill of lading is a contract including a receipt. It is a contract admitting *316the reception of certain goods, with an agreement to carry them to the port of discharge; and the only doubt in the case is, whether the terms of this agreement, as reduced to writing, in the bill of lading, can be varied by parol. If the actual reception of the salt by the master, was the. point in controversy, a different question would be presented. Such a case might come within the general rule of law, applicable to all receipts. But, in this case, it is agreed by all parties, that the salt was actually received by

the defendants, or their agent; and the only ^question is, whether the agreement, for the transportation of the salt thus admitted to be received, can be changed by parol testimony.

The legal effect of this agreement, as reduced to writing, is, to carry the goods from Buffalo to Cleveland by the most direct route conveniently adapted to that purpose, dangers of the seas, etc., excepted. The defendants seek to avoid this legal effect and the consequences resulting from its violation, by showing that it was a part of the agreement that the schooner might touch at Otter Creek, a place out of the regular course, and where she could not go except by such agreement, and that the master refused to receive the salt upon any other terms. This evidence comes within the direct operation of the rule that you shall not engraft a parol condition upon a written contract. Serg. & R. 469; B. Mon. 535; 1 Starkie, n. v. 361.

We consider this point of the base settled in 2 Conn. 9. “ Where the master of a vessel, receiving goods for transportation, gave the shipper a writing, acknowledging the receipt of goods, and stating that they were to be transported to the place of destination as customary freight,, dangers of the seas excepted, it was held that a parol agreement between the shipper and master, before and at the time of giving the writing, as to the mode of stowing the goods, was inadmissible to show the terms of shipment, as all such communications between the parties are to be considered as merged in the writing.”

But it is said that the court, in this case, admitted parol evidence of the custom of navigating Lake Erie. Evidence of this chaiae- . ter is admissible, not to vary the contract, but for the purpose of carrying it into execution, • as understood by the parties. This principle is laid down with great precision and force in 9 Wheat. 587. There is no rule of law better settled, or more salutary in its application to contracts than that which precludes the admission *317of parol evidence to contradict or substantially vary the legal import of a written agreement. Evidence of usage or custom is, however, never considered of this character, but is received for the purpose of ascertaining the sense and understanding of parties by their contracts, which are made with reference *to such usage or custom; for the custom then becomes a part of the contract, and may not improperly be considered the law of the contract; and it rests upon the same principles as the doctrine of the lex loci. All contracts are to be governed by the law of the place where they are to be performed; and this law may be, and usually is, proved as matter of fact. See Doug. 511; 4 Mass. 155; 3 Day, 146; 1 Caine, 43; 18 Johns. 220; 5 Cranch, 492.

The evidence of the collector of the port, to show that the vessel was at liberty to visit the Canada shore, without incurring a forfeiture, can have no effect as between these parties, and is also liable to the same objections as the other testimony rejected.

Motion overruled.