Oral evidence is admissible in this case for the purpose of applying the words of the written contract of the parties to the subject matter to which it relates, that is, to show what debts were properly included within its terms as the debts of Childs, Cotton & Co. To this extent, the written agreement called for extrinsic proof. As the bond contains no statement or schedule of the debts of the firm, which the defendants stipulated to pay, it is necessary to resort to proof dehors the instrument in order to determine whether a particular debt falls within the terms of the written contract. It is therefore competent for the plaintiff to prove by paroi evidence that he had paid a claim which might properly be enumerated among the debts of Childs, Cotton & Co.

*262But beyond this the plaintiff cannot go. He cannot be permitted to prove that debts other than those due from that firm were intended by the parties to have been included within the terms of their agreement, because it would infringe on the elementary rule, that a written agreement cannot be varied or extended by a resort to oral testimony. To show that the condition of the bond was designed to comprehend something different from and more than the language imported, into which the parties had deliberately put their contract, would be a palpable violation of the salutary rule, which makes the written words the final and conclusive evidence of their intent. The debts which were due and owing from the two firms of Childs & Cotton and Childs, Cotton & Co. were entirely distinct and independent of each other. In legal contemplation, they each constituted a separate class or subject of indebtment, to the same extent as if the successive copartnerships had been composed of entirely different persons. They formed distinct grounds of action and of set-off, and could not be united either in support or defence of a suit at law. To permit the plaintiff to show that by the written agreement to pay the debts of one firm the parties intended also to include those due from the other would be equivalent to the admission of evidence to prove that an agreement in writing to pay the debts of A. was designed also to embrace those which were due from B.

It was urged by the counsel for the plaintiff that the debts due from the old firm of Childs & Cotton had been in effect converted into debts of the new copartnership by the agreement of the latter to assume and pay all the debts of the former, which was entered into at the time the new firm was formed by the admission of the defendant Walker as a member. But the difficulty in the way of maintaining this position is, that it requires us to put a strained construction on the language of the written contract, in order to meet the apparent equity of the plaintiff’s case, as disclosed by the paroi testimony. The debts of the old firm were not changed or affected in any way by the agreement among the members of the old and new firms as to their payment. They were still outstanding debts, for which *263the old copartnership only was liable. It is very doubtful whether the creditors of that firm could have maintained an action against the new partnership to recover their debts. Certain it is that a promise to pay all the debts of a copartnership withDut any specification of the names or number of the creditors or the amount due to them respectively, and without any evidence of an election by the creditors to look to the new firm as their debtors, did not make the several persons to whom debts were dne from the old firm creditors of the new copartnership. It would not be a promise by the party sought to be charged to the persons claiming the benefit of the promise. Dow v. Clark, 7 Gray, 198, 201. The agreement in the present case amounted to nothing more than an executory contract by the new copartnership with the old firm to assume and pay their debts; but it did not convert the latter into debts due from the new copartnership so as to bring them within the terms of the stipulation contained in the conditions of the bond, and render the defendants liable to the plaintiff in this action. This view of the meaning of the contract between the parties, as expressed in the bond, derives great strength from the language there used in describing the debts for which the defendants made themselves liable. They did not agree to assume any general indebtment of the firm, or to discharge or perform the contracts into which they had entered, but bound themselves to pay only the notes and accounts held by various persons against the firm of Childs, Cotton & Co., at such times as the said notes and accounts became due and payable, or hold the plaintiff harmless therefrom. Under a stipulation so specific, pointing directly to debts due to creditors of the new firm only, it is impossible to hold that the parties could have intended to include debts due from another and distinct partnership, for the payment of which the copartnership of Childs, Cotton & Co. was bound by an executory agreement with that firm, but to which its creditors were not a party.

Judgment for the defendants.