Assent may be indicated by acts as well as by words, and an expression which primarily indicates merely assent to receive a performance promised by the offeror may also justify an inference on the part of the offeror that the offeree undertakes to render comiter-performance:38 This double effect of an acceptance, as not only an expression of assent but also a counter-promise has already been noted.39 Where the offer clearly states the undertaking which the offeror requests as consideration for his offer there can be no doubt that any expression of assent by the offeree has this double effect. Where the offer is not thus clear, it is a question of construction what the natural meaning of the words and acts of the parties may mean. Taking title to goods with knowledge that they are offered at a certain price indicates a promise to pay that price.40 So that where goods which have not been ordered are sent and the buyer takes the goods, he impliedly agrees to pay for them.41 Not infrequently an agreement in terms states merely that one party will buy or that he will sell certain goods without stating any correlative obligation by the other party. If the parties were purporting to make a contract it will generally be a correct implication of fact to assume' the existence of the correlative promise.42

37 In Howard v. Daly, 61 N. Y. 362, 19 Am. Rep. 286, an offer was sent by the defendant to the plaintiff for a theatrical engagement in the form of a contract executed by the defendant with a duplicate which be requested the plaintiff, if she accepted, to sign and return. The plaintiff promptly signed the duplicate and deposited it in the defendant's letter box at his theatre, which was sometimes used for such purposes. It was held that a contract was completed although the duplicate never reached the defendant. in Holmes v. Myles, 141 Ala. 401, 37 So. 588, an acceptance of an option left at the house of the party giving the option was held effectual though he had gone to the woods and received no actual notice within the stipulated time. In Sherwin v. Nad. Cash Register Co., 5 Col App. 162, 38 Pac. 392, an offer sad revocation were received by the offeree in tin same mail. The court held the revocation effectual though there was no evidence which letter was in fact read first. This holding necessarily involves the conclusion that the possession of the revocation made it effectual. Similarly in the Scotch case of Dumnore p. Alexander, 9 Shaw & D. 100 (Sees. Cas.) Langdell's Cas Cont. (2d ed.) 121, letters of acceptance and rejection were simultaneously received and it was held that they must be treated as one communication.

38Pittsburgh Plate Glass Co. v. H. Neuer Glass Co., 253 Fed. 101, 165 C. C. A. 61. In Grossman v. Schenker, 206 N. Y. 466, 469, 100 N. E. 39, the court said:

"A contract includes not only what the parties said but also what is necessarily to be implied from what they said. Milliken v. Western Union Tel. Co., 110 N. Y. 403, 408,18 N. E. 251, 1 L. R. A. 281. Thus the words 'cash on delivery' with no other promise to pay 'imply a promise and create an obligation' to make payment upon delivery. Justice v. Lang, 42 N. Y. 493, 1 Am. Rep. 576. So the word 'sold' in a written agreement implies not only a contract to sell but also a contract to buy; Butler v. Thomson, 92 U. S. 412, 414, 23 L. Ed. 684, and a contract to buy with no express promise to Bell implies the latter obligation. Hudson Canal Co. v. Penn. Coal Co., 75 U. 8. [8 Wall] 276, 289, 19 L. Ed. 349. 'What is implied in an express contract is as much a part of it as what is expressed.' Bishop on Contracts [2d ed.], Sec. 241; for 'the law is a silent factor in every contract.' Long v.

Straw, 107 Ind. 94, 95, 6 N. E. 123, 7 N- E. 763.

A mutual agreement implies an offer and acceptance, or a promise for a promise in some form, and if, as alleged, it was 'mutually agreed . . . that the defendants would pay to the plaintiff the sum of $600, for such superintendence,' necessarily there was not only an express promise by the defendant to pay, but also an implied promise by the plaintiff to superintend. Allen v. Patterson, 7 N. Y. 476, 479, 57 Am. Dec. 542; Marie v. Garrison, 83 N. Y. 14, 23; Hadden v. Dimick, 31 How. Pr. 196, 226; Stilwell v. Ocean Steamship Co., 5 N. Y. App. Div. 212, 214; Jones & Co v. Binford, 74 Me. 439; Foulks v. Falls, 91 Ind. 315, 320." See also Baltimore Breweries Co. v. Callahan, 82 Md. 106, 33 Atl. 460; C. M. Cecil Co. v. C. D. Wood Electric Co., 103 N.Y. Misc. 687,170 N.Y. Supp. 962.

39See supra, Sec. 65; and infra, Sec. 1293.

40 Dexter v. Filmore, (Vt. 1918), 102 Atl. 1048.

41See infra, Sec. 91.

42 Cold Blast Transportation Co. v. Kansas City etc. Co., 114 Fed. 77, 62 C.C.A. 25, 57 L. R. A. 698; Lima Locomotive Ac. Co. v. National Steel Castings Co., 155 Fed. 77, 83 C C A. 593, 11 L. R. A. (N. S.) 713; Sterling Coal Co. p. Silver Springs, 162 Fed. 848, 89 C C. A. 520; Jenkins v. Anaheim Sugar Co., 247 Fed. 958, 961, 160 C C A. 658; Pittsburgh Plate Glass Co. v. H. Neuer Glass Co., 253 Fed. 161,165 C. C. A. 61. In Ziehm v. Frank Steil Brewing Co., 181 Md. 582, 102 Atl. 1005, 1007, the court said (citing Minnesota Lumber Co. p. Whitebreast Coal Co., 180 111 86, 43 N. E. 774, 31 L. R. A. 529; Wells v. Alexandre, 130 N. Y. 642,29 N. E. 142, 16 L. R.A.218):

"The general rule ... is to the effect that an accepted offer to furnish or deliver such articles of personal property as shall be needed, required, or consumed by the established business of the acceptor during a limited time is binding and may be enforced, because it contains an implied agreement of the acceptor to

More specifically, a seller who takes a written order or agreement to buy, thereby not only assents to receive the buyer's promise, but also himself impliedly agrees to sell.43 The receipt of such an order by a commercial traveler, however, carries with it no such implication. Unless his authority to make contracts, not simply to take orders is shown, no contract arises until acceptance of the order is sent to the buyer by the principal.44 The same question may arise in agreements with employees. The only express promise may be to employ or to serve. Whether the promise is gratuitous or is supported by an implied counter-promise is a question of fact in each case.45 Where a contract of employment for a definite time is made and the employee's services are continued after the expiration of the time, without objection, the inference is that the parties have assented to another contract for a term of the same length with the same salary and conditions of service; 46 following the analogy of a purchase all articles that shall be required in conducting hie business during the time named from the party who makes the offer."