1 Boardman v. Spooner, 13 Allen, 361. And see Warren v. Wheeler, 8 Met. 97; Dutton v. Gerrish, 9 Cush. 89; Raymond v. Raymond, 10 Cush. 134; Howe v. Walker, 4 Gray, 318; Galpin v. Atwater, 29 Conn. 93 (1860), reviewing the cases.

2 Dunham v. Barnes, 9 Allen, 352 (1864) ; Hazard v. Loring, 10 Cush. 267. In the latter case, Bigelow, J., said: "The rule that parol evidence is not admissible to vary, explain, or control a written contract, is not applicable to mere bills of parcels, made in the usual form, in which nothing appears but the name of the vendor and vendee, the articles purchased with the prices affixed, and a receipt of payment by the vendor. These form an exception to the general rule of evidence, being informal documents, intended only to specify prices, quantities, and a receipt of payment, and not used or designed to embody and set out the terms and conditions of a contract of bargain and sale. They are in the nature of receipts, and are always open to evidence, which proves the real terms upon which the agreement of sale was made between the parties. 1 Cowen & Hill's note to Phil, on Evid. 385, n. 229; 2 ib. 603, n. 295; Harris v. Johnston, 3 Cranch, 311; Wallace v. Rogers, 2 N. H. 506; Bradford v. Manly, 13 Mass. 139; Fletcher v. Willard, 14 Pick. 464." A bill of parcels may be shown by parol evidence to have been given by way of mortgage only. Caswell v. Keith, 12 Gray, 351 (1859).

3 Browning v. Haskell, 22 Pick. 310. See also Keyes v. Dearborn, 12 N. H. 52.

§ 823. But in consideration of the difficulty of comprehending, within the terms of a contract, all that the parties intend, and from the mischief which might often result from too rigid and literal an interpretation thereof, a modification has been introduced in cases where the language employed is either technical, ambiguous, or obscure. In such cases parol evidence is admissible not to contradict or vary the terms of a written contract, but either to explain and interpret what were otherwise doubtful; or to supply some deficiency.1 Thus, parol evidence of usage is admissible to explain the terms of a contract.2 So, the testimony of experts is admitted to explain technical terms, either local or provincial, or to interpret and decipher characters and signs, or to translate from foreign languages.8 So, also, contemporaneous writings, relating to the same subject-matter, are admissible in evidence.4 And parol testimony is admissible to show that a written contract was delivered conditionally, to operate as an agreement only upon the happening of a certain contingency,5 or not until the happening of a given event,6 but not that a bill or note should be renewed;7 nor for the purpose of postponing the time for payment out of a fund within the control of the maker of the note.1 So, also, parol evidence may be given to explain facts and circumstances to which the contract relates;2 and persons or property mentioned therein may be identified when designated by nicknames, by which they are not commonly known.3 So, also, oral evidence is competent to show that a mortgage, expressed to be to secure payment of a stated amount, was only given to secure the mortgagee for indorsing a note for the mortgagor, made at the same time, and for the same amount, as the mortgage.1 So, also, if there be an ambiguity as to which of two or more persons or things be intended, it may be elucidated by parol evidence; or, if there be a declaration by one party, assented to by the other, of the meaning intended to be given to certain terms or clauses, when such term or clause is obscure or ambiguous,2 parol evidence of such fact may be given. So, also, whatever goes to limit the terms of a contract may be given in evidence; as printed rules on the walls of a horse bazaar, limiting the vendor's liability, on a warranty of a horse, to a certain time.8 So, where a broker made an entry of a sale in his books without mentioning that it was a sale by sample, it was held that parol evidence of such fact was admissible, it appearing that no bought and sold note had been given.4 So, also, a new agreement in respect to the subject-matter of the contract,5 and additional thereto,6 may be proved by parol, if it do not contradict the terms of the original agreement.1 Thus, where A., by a written instrument, conveyed property to B. in consideration of a certain sum paid therefor, an additional oral agreement may be shown to repay the sum, on the happening of a certain event.2 So, the time of performance of an agreement necessarily made in writing under the statute of frauds, may be proved to have been enlarged by a subsequent oral agreement.3 So parol evidence of a verbal agreement is competent, although contracts or other instruments in writing have been executed in pursuance of such agreement, and by way of partial performance thereof.4 So, where the plaintiff conveyed to defendant a house by deed with a covenant against incumbrances, and occupied it afterwards for a certain time, parol evidence that the plaintiff was to possess it rent free, and that defendant agreed to pay the taxes assessed before the conveyance, is not contradictory to the deed, and is admissible.5 So parol evidence is admissible to correct an error in the name of the payee of a written order, where it is so connected with the testimony that the real owner may be clearly ascertained.6

1 Mallory v. Tioga Railroad, 3 Keyes, 354 (1867)

2 Huntley v. Woodward, 9 Gray, 86 (1857).

3 Clark v. Houghton, 12 Gray, 38 (1858).

4 Spurr v. Andrew, 6 Allen, 420 (1863).

5 Young v. Austen, Law R. 4 C. P. 553 (1869). So parol evidence is inadmissible to show that the drawer of a bill of exchange, at the time he signed the same, entered into a contract under which the payment was to be made at a different time and in a different manner from that which the bill imports. Abrey v. Crux, Law R. 5 C. P. 37 (1869).

1 1 Greenl. on Evid. § 278, et seq. See also Doe v. Hiscocks, 5 M. & W. 363, 367, where the matter is ably discussed by Lord Abinger; Hoadly v. M'Laine, 10 Bing. 482; 4 Moo. & S. 340; Hasbrook v. Paddock, 1 Barb. 635. The rule is very well stated by Wells, J., in Stoops v. Smith, 100 Mass. 63. In an action on a written contract for the manufacture and delivery of "horn chains," oral evidence is admissible to show that the parties intended by " horn chains" chains made of hoof and horn. Swett v. Shumway, 102 Mass. 365 (1869).