The contract, as originally entered into, cannot at Law be altered by evidence of a parol variation in favour of either plaintiff or defendant (a) ; but an action may lie on a parol agreement, which varies, but does not actually conflict with, the terms of the written instrument (b) ; and parol evidence may be admitted to prove that an agreement, absolute in form, was intended to operate only on the happening of certain contingencies (c).

Section 5

No parol variation allowed at Law.

As respects the reception of parol evidence in order to explain agreements of doubtful or ambiguous meaning, the following seems to be the general result of the authorities. The Courts will always, if necessary, receive evidence to enable them to decipher, or, if written in a foreign language, to interpret, the instrument; that is, to ascertain what are the expressions, or the English equivalents to the expressions, which the parties have actually used. They will also receive parol evidence of the meaning which local custom (d),

Parol evidence, how far admissible in explanation of contract.

(2) Thomas v. Broun, (1876) 1 Q. B. D. 714; 45 L. J. Q. B. 811.

(a) Goss v. Lord Nugent, (1833) 5 B. & Ad. 58; 2 L. J. N. S. K. B. 127; sup. p. 123; Henson v. Coope, (1841) 3 Sc. N. R. 48; Stead v. Daivber, (1839) 10 A. & E. 57 ; Marshall v. Lynn, (1840) G M. & W. 109 ; Emmet v. Dewhurst, (1851) 3 M. & G. at pp. 596, 597 ; 21 L. J. Ch. 497 ; Canham v.Barry, (1855) 15 C. B. 597; 24 L. J. C. P. 100; Noble v. Ward, (1SG7) L. R. 2 Ex. 135; 36 L. J. Ex. 91 ; Sanderson v. Graven, (1875) L. R. 10 Ex. 234; 44 L. J. Ex. 210; Anker v. Franklin, (1880) 43 L. T. 317; New London Credit Syndicate v. Neale, 1898, 2 Q. B. 487 ; 67 L. J. Q. B. 825.

(b) Nash v. Armstrong, (1861) 10 C. B. N. S. 259 ; 30 L. J. C. P. 286.

(c) See sup. p. 254; also Kerne Bay, §c. Co. v. Hutton, 1903, 2 K. B. 683 ; 72 L. J. K. B. 879.

(d) Smith v. Wilson, (1832) 3 B. & Ad. 728; Doe v. Benson, (1821) 4 B. & Ald. 588, where evidence was admitted to show that by Lady-day was meant old Lady-day; Tudgay v. Sampson, (1874) 30 L. T. 262, evidence of custom admitted to explain terms in agricultural lease; Tucker v. Linger, (1883) 8 A. C. 508 ; 52 L. J. Ch. 941, where evidence of a custom for tenants to remove and sell flints, turned up in cultivation, was allowed to show that they were not included in a reservation of mines and minerals. And see as to evidence of custom, generally, notes to Wiggles-worth v. Dallison, (1779) 1 Sm. L. C. 11th ed. 545.

Or professional or trade usage (e), or the former practice of the parties themselves (f), has attached to particular expressions: so as, in fact, to ascertain what is (with reference to the particular subject-matter of the contract) their strict and primary meaning (g) ; - unless such a construction would be inconsistent with the terms of the instrument (h), or some express provisions of the Legislature; for instance, local custom cannot vary the statutory meaning of expressions referring to weights and measures (i) ; - or to annex any customary incidents to the contract which are not expressly or impliedly excluded by the terms of the written instrument (k). Where construing the expressions according to their strict and primary meaning would render them meaningless with reference to extrinsic circumstances, the Courts will receive parol evidence of the circumstances and situations of the parties and the state of the property at the date of the agreement, for the purpose of ascertaining whether such expressions have not been used in some secondary sense consistent with such circumstances, etc. (/). So, where an agent contracts, parol evidence is admissible to prove who is the principal (m) ; or to show that the apparent agent is himself the principal (n). And where, as respects all or any part of the subject-matter of the contract (o), or the identity of places, documents (p), or persons (q) referred to, there is a latent ambiguity - that is, where the words of the agreement, though certain in point of grammatical construction and apparently definite, are rendered of doubtful (r) application by circumstances which appear aliunde (s), or upon the face of the agreement itself (t)-parol evidence of the intention of the parties at the date of the agreement is admissible, in order to identify the estate, document, plan or other thing or person intended; but such evidence is not admissible in aid of a patent ambiguity; i.e., an ambiguity which is either directly suggested by the terms of the instrument (u), or is occasioned by the grammatical uncertainty of the expressions therein used; nor, a fortiori, to control the clear effect of an unambiguous instrument (x). Generally (y), extrinsic evidence is always admissible, not to vary or contradict the contract, but to show what facts the parties had in their minds and were negotiating about, and to enable the Court to ascertain the nature and qualities of the subject-matter of the instrument, in other words, to identify the persons and things to which the instrument refers, and to show the sense the words bear with reference to the surrounding circumstances, of and concerning which the words were used; but evidence of such facts as only tend to show that the writer intended to use words bearing a particular meaning will not be admitted.

(e) Clayton v. Gregson, (1836) 4 N. & M. 602; Hutchison v. Bowker, (1839) 5 M. & W. 535; and see Lewis v. Marshall, (1844) 8 Sc. N. R. 477, 493; 13 L. J C. P. 193 ; Sotilichos v. Kemp, (1848) 3 Ex. 105 ; 18 L. J. Ex. 36; Malcolm v. Scott, (1850) 3 M. & G. 29 ; 20 L. J. Ch. 17 ; Smith v. Thompson, (1849) 8 C. B. 44 ; 18 L. J. C. P. 314 ; Simpson v. Margit-son, (1847) 11 Q. B. 23, 32 ; 17 L. J. Q. B. 81 ; Fawkes v. Lamb, (1862) 8 Jur. N. S. 385 ; 31 L. J. Q. B. 98 ; Newell v. Radford, (1867) L. R. 3 C. P. 52 ; 37 L. J. C. P. 1 ; Holt v. Collyer, (1881) 16 Ch. D. 718, 720 ; 50 L. J. Ch. 311. Where it is intended to give general evidence as to the meaning of words in a contract, there should be a distinct averment on record as to the particular words, and the precise technical or trade meaning which it is intended to attribute to them : Sultou v. Civeri.