As we have seen, custom is a usage which has acquired the force of law 43 and ignorance of the law will not excuse. "A general custom is the common law itself, or part of it." Such a general custom for instance, as days of grace on a note (now abolished in some states) so pervaded the whole commercial world that it was universally understood to enter into every note. In such a case a party would not be heard to say that he was ignorant of the custom.44
"Doubtless if a custom is ancient, very general and well known, it will often be a presumption of law that the party had knowledge of it.45 It would seem, however, that upon principle, for a party to be bound by a local usage, or a usage of a particular trade or profession, he must be shown to have knowledge or notice of its existence. * * * Usage is engrafted upon a contract or invoked to give it a meaning, on the assumption that the parties contracted in reference to it; that is to say, that it was their intention that it should be a part of their contract wherever their contract in that regard was silent or obscure. * * * No usage is admissible to influence the construction of a contract unless it appears that it be so well settled, so uniformly acted upon and so long continued as to raise a fair presumption that it was known to both contracting parties, and that they contracted in reference thereto. There must be some proof that the contract had reference to it, or proof arising out of the position of the parties, their knowledge of *the course of business, their knowledge of the usage, or other circumstance from which it may be inferred or presumed that they had reference to it." 46
42 Citing Dyer v. Sutherland, 75 111. 583.
43 Sec. 221 supra.
44 Walls v. Bailey, 49 N. Y, 472 (1872).
45See Steldtmann v. Lay Co., 234 111. 89 (1908).
"The principle governing particular customs or trade usages is as follows: 'The elements of antiquity need not be shown in the case of a usage or custom of trades. All that is required is to show that it is established, that is, that it has existed a sufficient length of time to have become generally known.' ' Particular usages and customs of trade or business must be known by the party to be affected by them, or they will not be binding, unless they are so notorious, universal and well established that his knowledge of them will be conclusively presumed.' " 47
Proof of the custom is admissible on the theory that it explains an ambiguity in the agreement.48 In Atkinson v. Truesdell, 127 N. Y. 234 (1891), the rule is stated that " parol evidence may be given as to the uniform, continuous and well-settled usage and custom pertaining to the matters embraced in the contract, unless such usage and custom contravene a rule of law,49 or alter or contradict the expressed or implied terms of a contract free from ambiguity."
46 Walls v. Bailey, 49 N. Y. 473, 474, 476 (1872). See Sec. 224 infra, as to proof of custom.
47Arkadelphla Lbr. Co. v. Henderson, 84 Ark. 389 (1907), (citing 12 Cyc. 1034, 1041; and Arkansas cases).
48Walls v. Bailey, 49 N. Y. 468 (1872).
A custom is " to be established or negatived in all its essentials as well as to knowledge as to any other, by the same character and weight of evidence as are necessary to maintain other allegations of fact. It may be established by presumptive as well as by direct evidence. Nor, on the other hand, is it exempt from the difficulty that a presumption may not prevail against direct evidence to the contrary of it. The jury may presume, from all the circumstances of the case, that knowledge or notice existed. " As for instance, that the usage existed for many years, that the party resided at the place where the custom existed, or that the party was himself of the trade or profession in which the custom existed.50
"It is for the jury then, under proper instructions from the court, to take all the evidence in the case; that as to the existence, duration and other characteristics of the custom or usage, and that as to the knowledge thereof of the parties; and therefrom to determine whether there is shown a custom of such age and character, as that the presumption of law will arise that the parties knew of, and contracted in reference to it, or whether the usage is so local and particular, as that knowledge in the party to be charged must be shown affirmatively or may be negatived."51
A single act or transaction is not enough to warrant the inference that such act or transaction is customary.
49A custom contravening a positive statute is invalid. Deadwyler v. Karow, 131 Ga. 227 (1908).
50 Walls v. Bailey, 49 N. Y. 476 (1872).
Walls v. Bailey, 49 N. Y. 477 (1872).
While there has been some controversy as to whether a local custom may be shown by a single witness, the rule seems to have been settled by modern decisions that the testimony of one witness may be sufficient.52 And it may be proved even by the party's own testimony.53 To establish a custom it is not necessary that all the witnesses on both sides must agree about it. If they differ as to its existence in the same place or in all places it raises a question for the jury.54