Knapp v. Harden, 6 C. & P. 745; Deshon v. Merchants Ins. Co. 11 Met 190; Edwards v. Goldsmith, 16 Penn. St. 43; Coates v. Sangston, 6 Md. 121; Knight v. Knotts, 8 Rich. Law, 36. Also Heatherley v. Record, 12 Texas, 49.

(i) In Colbourn v. Dawson, 10 C B. 765, 4 Eng. L. & Eq. 378, the plaintiffs wrote to the defendant: "We are doing business with B, and require a guaranty to the amount of £200, and he refers us to you." Defendant wrote in answer: "I have no objection to become security for B, and subjoin a memorandum to that effect." The memorandum subjoined was: "I hereby engage to guaranty to Messrs. Colbourn, iron-masters, £200 for iron received from them for B, as annexed." Held, that these three documents should be read together, and that the words, •' we are doing business," taken with the rest, showed that the consideration for the defendant's undertaking was that the plaintiff should continue to sup1 Also a collateral undertaking. Chapin v. Dobson, 78 N. Y. 74, where the authorities are collated and reviewed.

* to affect a third party who relied upon the contract, and knew nothing of these other writings.

Recitals in an instrument may be qualified or contradicted by extrinsic evidence, if the law of estoppel does not prevent. So the date of an instrument, (j) or if there be no date, the time when it was to take effect, which may be other than the day of delivery; (k) or the amount of the consideration paid, (l) may be varied by testimony; but if a note given for land is sued, the promisor cannot show in defence that the deed described a less quantity of land than had been stipulated. (m) And an instrument may be shown to be void and without legal existence or efficacy, as for want of consideration, (n) or for fraud, (o) or duress, or any incapacity of the parties, (p) or any illegality in the agreement. (q) In the same way extrinsic evidence may show a total discharge of the obligations of the contract; or a new agreement substituted for the former, which it sets aside;(r) *or that the time when, (s) or the place where, (t) certain things were to be done, had been changed by the parties; or that a new contract, which was additional and supplementary to the original contract, had been made (u);1 or that damages had been waived, (v) or that a new ply B with goods, and that there was therefore a good consideration. See also Hunt v. Frost, 4 Cush. 64; Hanford v. Rogers, 11 Barb. 18; Shaw v. Leavitt, 3 Sandf. Ch. 168; Gammon v. Freeman, 81 Me. 243; Kenyon v. Nichols, 1R. I. 411.

(j) Breck v. Cole, 4 Sandf. 79; Abrams v. Pomeroy, 13 Ill. 133; Hall v. Cazenove, 4 East, 477. Where, however, the date is referred to in the body of the instrument, as fixing the time of payment, as where there is a promise to pay money or to do some act "in sixty days from date," the date cannot be altered or varied by parol evidence. Joseph v. Bigelow, 4 Cush. 82.

(k) Davis v. Jones, 17 C. B. 625.

(l) Clifford v. Turrell, 1 Younge & C. Cas. in Ch. 138; Rex v. Scammonden, 3 T. R. 474; Belden v. Seymour, 8 Conn. 304. As to the effect of a recital in a deed of conveyance of the payment of the consideration-money, as evidence of such payment, the English and American authorities differ, the former holding such recital to be conclusive evidence, and the latter only prima facie. See the cases collected ana arranged in 1 Gr. Ev. § 26, n. (l)

(m) Bennett v. Ryan, 9 Gray, 204.

(n) Erwin v. Saunders, 1 Cowen, 249; Foster v. Jolly, 1 Cromp. M. & R. 708 The case of Bowers v. Hurd, 10 Mass. 427, so far as it contains a contrary doctrine, has been overruled. See Hill v. Buckminster, 6 Pick. 891; Parish v. Stone, 14 id. 198.

(o) Erwin v. Saunders, 1 Cowen, 249; Van Valkenburgh v. Roun, 12 Johns. 837.

(p) Mitchell v. Kingman, 6 Pick. 431. Subscribing witnesses to a deed derive from their being witnesses no authority to give their opinion as to the competency of the party to contract, by reason of sanity or other capacity; the execution of the deed being all that is attested by them, 40 Penn. St. 474.

(q) Collins v. Blantern, 2 Wilson, 347.

(r) Munroe v. Perkins, 9 Pick. 298; Goss v. Lord Nugent, 5 B. & Ad. 58; Davis v. Tallcott, 2 Kern. 184.

(s) Keating v. Price, 1 Johns. Cas. 22; Dearborn v. Cross, 7 Cowen, 48; Neil v. Cheves, 1 Bailey, 537; Cuff v. Penn, 1 M. & S. 21.

(t) Robinson v. Batchelder, 4 N. H. 40.

(u) Jeffery v. Walton, 1 Stark. 267. See also Emerson v. Slater, 22 How. 28.

(v) Flemming v. Gilbert, 3 Johns. 628.

1 But a subsequent agreement not referring to, or able by its terms to be connected with, a contract does not vary the latter. Gavigan v. Evans. 46 Mich. 597.

consideration, in addition to the one mentioned, has been given, if it be not adverse to that named in the deed. (w) And if no consideration be named, one may be proved. (x)

A receipt for money is peculiarly open to evidence. It is only prima facie evidence either that the sum stated has been paid, or that any sum whatever was paid. (y) It is in fact not regarded as a contract, and hardly as an instrument at all, and has but little more force than the oral admission of the party receiving. But this is true only of a simple receipt. It often happens that a paper which contains a receipt, or recites the receiving of money or of goods, contains also terms, conditions, and agreements, or assignments. Such an instrument, as to everything but the receipt, is no more to be affected by extrinsic evidence than if it did not contain the receipt; but as to the receipt itself, it may be varied or contradicted by extrinsic testimony, in the same manner as if it contained nothing else. (z)

If a contract refer to principles of science, or art, or use, the technical phraseology of some profession or occupation, or common words in a technical sense, or the words of a foreign language, their exact meaning may be shown, as we have already remarked, by the testimony of "experts," who are persons possessing the peculiar knowledge and skill requisite for the interpretation of the contract. (a) 1 It may be added,