It is essential to the formation of a contract that the acceptance conform to the requirements of the offer. But if there is an ambiguity in the terms of the offer, an acceptance which appears to coincide with the offer may in reality vary from it.5 Of such cases Turner v. Webster 6 is an excellent example. The plaintiff offered to watch over certain property for the defendant for "$1.50 per day, and nights the same," meaning thereby $1.50 for a day of twelve hours, or $3.00 for a day of twenty-four hours. The defendant's agent understood the offer to mean $1.50 per day of twenty-four hours, and under that misunderstanding the plaintiff was employed. The promise of the plaintiff being to do certain work in consideration of $3.00, and that of the defendant to pay $1.50 for such work, it is obvious that neither promise was supported by the consideration which it required and that the contract was therefore void. But the plaintiff having rendered services in reliance upon the supposed contract right to compensation was justly held to be entitled to restitution in value to the extent of the benefit derived by the defendant therefrom.1

1 Hogg v. Laster, 1892, 56 Ark. 382; 19 S. W. 975; Stock v. Stoltz, 1891, 137 111. 349; 27 N. E. 604; Walker v. Taylor, 1901, 28 Colo. 233; 64 Pac. 192; Reeves' Estate v. Moore, 1892, 4 Ind. App. 492; 31 N. E. 44; McClure v. Lenz, 1907, 40 Ind. App. 56; 80 N. E. 988; Smith 9. Johnson, 1876, 45 la. 308; Wyley v. Bull, 1889, 41 Kan. 206; 20 Pac. 855; Andrus v. Foster, 1845, 17 Vt. 556; Martin v. Martin, 1900, 108 Wis. 284; 84 N. W. 439; 81 Am. St. Rep. 895.

2 Keegan v. Estate of Malone, 1883, 62 la. 208; 17 N. W. 461.

3 Rhodes v. Stone, 1892, 63 Hun 624; 17 N. Y. Supp. 561; Swires v. Parsons, 1843, 5 Watts & S. (Pa.) 357.

"When the relation of concubinage is incidental, and is not the motive and cause of the parties living together, the concubine can recover from the estate of the deceased, if it has been enriched by her industry." - Succession of Llula, 1892, 44 La. Ann. 61, 63; 10 So. 406. See also Succession of Pereuilhet, 1871, 23 La. Ann. 294, 295; 8 Am. Rep. 595, where the court said: "An employer cannot pay off a female employee by robbing her of her virtue."

4 Parker's Heirs v. Parker's Admr., 1859, 33 Ala. 459; Page v. Page, 1905, 73 N. H. 305; 61 Atl. 356; Moyer's Appeal, 1886, 112 Pa. St. 290; 3 Atl. 811; Williams v. Williams, 1902, 114 Wis. 79; 89 N. W. 835.

5 Rupley v. Daggett, 1874, 74 111. 351, (mistake as to price of mare). 6 1880, 24 Kan. 38; 36 Am. Rep. 251.

If the ambiguity relates to the identity of the subject matter of an offer rather than to its terms, the same result follows. Thus, where it appeared, in a contract for the sale of cotton "ex Peerless from Bombay," that there were two vessels bearing the name Peerless sailing from Bombay, and that the seller had in mind one ship and the buyer the other, the contract was void.2 But if it had further appeared that prior to the discovery of the misunderstanding and in reliance upon the supposed contract the buyer had paid the whole or a portion of the purchase price of the cotton, the seller would have been under an obligation to refund.3

So long as the transaction rests in parol, it may be shown that the offeree, in accepting the ambiguous offer, placed upon it the same interpretation as the offerer, in which case, of course, the contract would be valid and no quasi contractual obligation would arise. But when the ambiguity is carried into a written instrument, parol evidence will not be admitted to show what the parties meant unless the ambiguity is a latent one, i.e. not apparent on the face of the instrument but resulting from extraneous facts.4 An example of quasi contractual obligation resulting from a patent ambiguity in a written instrument is found in an early Wisconsin case:

Cole v. Clark, 1851, 3 Pinn. (Wis.) 303: The plaintiff, in consideration of five hundred dollars, agreed under seal to put in two waterwheels, "to drive each a run of stone in the flouring mills, and warrant the same, with two hundred inches of water to each wheel, to be measured at the bottom of the flume, to grind fifteen bushels per hour." The county judge charged the jury that if they found that both run of stone would grind the fifteen bushels per hour, the plaintiff had complied with the requirements of his contract. But the Supreme Court declared itself unable to take that view. "On the contrary," said Hubbell, C.J. (p. 305), "we are all of the opinion that it is too indefinite and uncertain to admit of any interpretation as a matter of law. The offer to introduce oral evidence to explain the understanding of the parties was properly rejected. Such evidence is admissible when there is a latent ambiguity, which is made to appear by extraneous facts, and which may be made clear by parol proof. But the ambiguity in this case is patent; it appears on the face of the instrument; and it arises not from the use of words of art, or technical phrases, nor from the existence of any custom or usage, but from the failure of the parties so to use common and plain words as to express any definite idea. They have not told us themselves what they did mean; whether each run of stone was to grind fifteen bushels per hour, or whether both were to do it, and so their instrument is wholly void. The judgment of the county court must be reversed for this cause, and the case must go back for a new trial. The plaintiff then can recover quantum meruit upon the common counts, and no more."

1 Accord: Peerless Glass Co. v. Pacific Crockery, etc., Co., 1898, 121 Cal. 641; 54 Pac. 101, ("freight allowance" on sale of goods); Tucker v. Preston, 1887, 60 Vt. 473; 11 Atl. 726, (terms of employment).

2 Raffles v. Wichelhaus, 1864, 2 Hurl. & C. 906.

3 See De Wolff v. Howe, 1906, 112 App. Div. 104; 98 N. Y. Supp. 262, (sale of goods; mistake in sampling order).

4 See Wigmore, "Evidence," Sec. Sec. 2470-2473.