§ 819. This subject comes more properly under that branch of law which treats of evidence, yet the subject of interpretation seems necessarily to require a brief outline, at least, of the doctrine of parol evidence affecting written agreements, in order to give it completeness.

§ 820. The rule of law on this subject is, that parol contemporaneous evidence is inadmissible to contradict or to vary the terms of a valid written instrument.1 This rule, although introduced in early times, when a seal accompanied every written agreement, and was often the only signature of the party, has still continued in force, and is applicable as well to simple contracts as to contracts under seal,2 and is not affected by a statute which allows a party to call the opposite party as a witness.3 Thus, if a party should make a written contract, or indorse a note, or draw a bill of exchange, in his own name, he could not discharge himself from personal liability by parol evidence that he was acting in the matter solely in the capacity of agent, since this would be to contradict the actual terms of the contract.4 And parol evidence that a contract, signed by

1 1 Phil. & Am. on Evid. 753 ; 2 Stark. Evid. 544, 548; Adams v. Word-ley, 1 M. & W. 379, 380; 1 Greenl. Evid. § 275; Boorman v. Jenkins, 12 Wend. 573; Miller v. Travers, 8 Bing. 244; Colwell v. Lawrence, 38 N. Y. 71 (1868).

2 Stackpole v. Arnold, 11 Mass. 31. See also Woollam v. Hearn, 7 Ves. 218; Hunt v. Adams, 7 Mass. 522.

3 Kelly v. Cunningham, 1 Allen, 473.

4 Higgins v. Senior, 8 M. & W. 844, 845; Gray v. Gutteridge, 1 M. & R. 618; Leadbitter v. Farrow, 5 M. & S. 345; Nash v. Towne, 5 Wall. 690 (1866) ; Ford v. Williams, 21 How. 287 (1858). But if a contract is signed "B., by C," parol evidence is admissible to show that B. was only an agent the plaintiffs jointly with the defendants, and apparently a joint undertaking by all the signers, was in fact signed by the plaintiffs as one party, and by the defendants as a second party, is inadmissible, as tending to contradict or control a written instrument.1 But a written contract may be superseded by a subsequent verbal agreement inconsistent with it.2 And it is held that a written contract of agency may be enlarged by proof of subsequent declarations and conduct of the principal.3 § 821. The object of interpretation is, as we have seen, to ascertain the intention of the parties. Whenever such intention is clearly and definitely expressed, no rules of interpretation are requisite, but only in cases where there is an ambiguity or deficiency in the record of such intention. These rules, however, would be often incapable of application, without the introduction of evidence in respect to certain facts and circumstances, the existence of which is presupposed by them. Many such facts and circumstances must necessarily exist, which, although entirely unrecorded, materially affect the nature and extent of a contract, and the situation of the parties;4 and in respect to these, parol evidence is admitted. Thus, when it becomes material to ascertain the purpose for which a writing was executed, if not inconsistent with its terms, it may properly be proved by parol.5 Where a contract is not reduced to writing, it is manifest that parol evidence is the only evidence which can be given, in respect to its nature, object, and extent.6 of A., and thus to charge A. as principal, although there is no intimation in the contract that B. was such agent. Lerned v. Johns, 9 Allen, 419 (1864).

1 Myrick v. Dame, 9 Cush. 248 (1852). In a suit by the payee of a promissory note, against one who indorsed it in blank at the time it was given, parol evidence is admissible to show the real nature of the transaction. Riley v. Gerrish, 9 Cush. 104 (1851).

2 Lulzbacher v. Davidson, 34 N. Y. Superior Ct. Rep. 145 (1871).

3 Hartford Fire Ins. Co. v. Wilcox, 57 111. 180 (1870).

4 Griffiths v. Hardenbergh, 41 N Y. 464 (1869).

5 Hutchins v. Hebbard, 34 1ST. Y. 24 (1865).

6 It is probable, also, that the rule excluding extrinsic evidence to affect written instruments applies only to controversies between the parties to the contract, and that strangers or third persons may contradict or control the letter from the lessor and an indorsement thereon by one of the lessees. The lessor there offered to prove the terms of the lease by parol evidence, but it was excluded on the ground that the agreement appeared to be in writing, and parol testimony was inadmissible to vary or modify its terms.1 So a written agreement for drawing stone "at the rate of one dollar and twenty-five cents per load of two tons each,,, fixes the rate by the ton, without regard to the number of tons actually drawn in one load; and cannot be varied by parol evidence.2 So evidence of an oral agreement of the mortgagor and mortgagee, immediately after the delivery of a mortgage of personal property, that the mortgagor shall retain the right to sell or exchange the property, is inadmissible to control the construction or effect of the mortgage.3 So, in an action to recover damages for a breach of a covenant against incumbrances, by reason of the existence of a right in a third person to cut and remove standing trees, oral evidence is inadmissible to prove that the parties both intended to except this right from the operation of the covenant, and that it was mutually understood between them that the trees were not to pass with the land.4 So it is not competent for the acceptor of a bill of exchange to show by parol that he accepted the bill on a condition then agreed on between him and the maker, that on a certain event which occurred the maker would renew the bill.6

§ 822. Inasmuch as the terms of a written contract manifestly contain a more deliberate and definite record of the intention and mutual understanding of the parties 1 than that loose talk which usually precedes a contract,2 the law has rightly insisted that the parties shall not contradict such an. instrument by parol evidence.3 Thus, where A. entered into a recitals in a contract, to which they are not parties. See Furbush v. Goodwin, 25 N. H. 446 (1852) ; Eaton v. Alger, 2 Keyes, 41, 45 (1865) ; Taylor v. Baldwin, 10 Barb. 587 (1850) ; Fuller v. Acker, 1 Hill, 473 (1841) ; Reynolds v. Magness, 2 Ired. 30; Woodman v. Eastman, 10 N. H. 359; Krider v. Lafferty, 1 Whart. 314; Evans v. Wells, 22 Wend. 345.