The terms of the offer may be such that the offer can be accepted only by doing some specified act; and it may not even require that notice of doing such act be communicated to the offeror.1 In subscriptions, the incurring of liabilities may be acceptance, consideration and performance in one, without a previous promise to incur them.2 An offer which by its terms is to be accepted by doing an act, has been said to be unenforceable because it lacks mutuality. The true ground of objection in this case is that such offer has not been accepted by doing the act which is at the same time the acceptance, the consideration, and the performance. If the contract is accepted by doing the act, no objection can be made to the contract upon the ground of want of mutuality.3 The same act amounts to acceptance, consideration, and performance. In terms of mutuality this is explained by saying that performance has eliminated the original want of mutuality,4 and as far as such contract has been performed, the rights of the parties are to be measured by its terms.5 In the sense in which this expression is used, it is perfectly true. The promise, lacking in so-called mutuality, is not supported by any consideration, is not legally binding; and in legal effect is merely an offer, although the parties may believe it to be a valid contract. It is, however, an offer which is to be accepted by the doing of an act, which act is at the same time acceptance and consideration. The doing of this act is the performance which eliminates the lack of the so-called mutuality.6 A's promise to convey whenever B should pay a certain amount, becomes binding when B pays such amount.7 A promise by A to sell to B, without imposing upon B any liability to buy, becomes enforceable if B pays part and tenders the balance,8 or if B accepts and tenders performance.9 A promise by A to pay to B, to apply on C's debt a certain sum for each thousand feet of logs delivered by C to B, intended to induce B to continue to give credit to C, is supported by sufficient consideration if B in fact gave such credit.10 So a promise by A, the father of X, to permit B, the great-grandfather of X, to keep X while B lived, is supported by sufficient consideration after B has in fact taken custody of X and supported him.11 A's expenditure of time and labor, with B's knowledge, in securing an "acceptable" tenant for property which A has leased to B, is consideration for B's prior promise to consent to the assignment of A's lease if A would secure a suitable tenant.12 A promise by A to construct a beer depot and to furnish beer therefrom to B, and to furnish beer to B without charge, if such depot was not built is valid, after B, in reliance thereon, has accepted beer from A.13

7 Bailey v. Austrian, 19 Minn. 465.

8 See Sec. 580.

9 Vicksburg Water-works Co. v. J. M. McGuffy Petroleum Co., 86 Miss. 60, 38 So. 302.

1 Atkinson v. Whitney, 67 Miss. 655, 7 So. 644; Cox v. Stokes, 156 N. Y. 491, 51 N. E. 316 [reversing, 78 Hun 331].

See Sec. 153 et seq.

See, for considerations of this sort, Offers Calling for a Consideration Other Than a Counter Promise, by Clarence D. Ashley, 23 Harvard Law Review 159.

2 See Sec. 157.

3 L'Amoreux v. Gould, 7 N. Y. 349.

4 Arizona. Little Butte Consolidated Mines Co. v. Girand, 19 Ariz. 4, 123 Pac. 309.

Arkansas. El Dorado Ice & Planing Mill Co. v. Kinard, 96 Ark. 184, 131 S. W. 460.

Iowa. Des Moines Valley Ry.v. Graff, 27 la. 99, 1 Am. Rep. 256.

Kentucky. Victoria Limestone Co. v. Hinton, 156 Ky. 674, 161 S. W. 1109.

Maine. Hay v. Fortier, 116 Me. 456, 102 Atl. 204.

Massachusetts. Goward v. Waters, 98 Mass. 596; Buffington v. McNally, 192 Mass. 198, 78 N. E. 309.

Minnesota. Staples v. O'Neal, 64 Minn. 27, 65 N. W. 1082.

Missouri. Underwood Typewriter Co. v. Century Realty Co., 220 Mo. 522, 119 S. W. 400.

North Dakota. Gile v. Interstate Motor Car Co., 27 N. D. 108, L. R. A. 1915B, 109, 145 N. W. 732; Murphy v. Hanna, 37 N. D. 156, L. R. A. 1918B, 135, 164 N. W. 32.

Oregon. Krausse v. Greenfield, 61 Or. 502, 123 Pac. 392; Oregon Home Builders v. Crowley, 87 Or. 517, 170 Pac. 718, 171 Pac. 214.

Washington. Gerard v. Seattle, 73 Wash. 519, 132 Pac. 227.

Wisconsin. Oconto Brewing Co. v. Cayouette, 138 Wis. 664, 120 N. W. 497.

5 Gile v. Interstate Motor Car Co., 27 N. D. 108, L. R. A. 1915B, 109, 145 N. W. 732.

6 Hall v. Olson, 58 Or. 464, 114 Pac. 638; Oconto Brewing Co. v. Cayouette, 138 Wis. 664, 120 N. W. 497.

7 Vanity Fair Co. v. Hayes, 31 R. I. 77, 76 Atl. 771.

8Watkins v. Davison, 61 Wash. 662, 112 Pac. 743.

9Sayward v. Houghton, 119 Cal. 545, 51 Pac. 853, 52 Pac. 44.

10 Schoening v. Maple Valley Lumber Co., 61 Wash. 332, 112 Pac. 381.

11 Wilkinson v. Lee, 138 Ga. 360, 75 S. E. 477.

A contract to furnish a "reasonable quantity" of certain goods after such are in fact furnished;14 a promise by a physician, B, who was employed by another physician, A, as an assistant, not to compete within that city for five years after the employment should cease, although the employment was terminable at the will of either party, if B was in fact employed and paid by A;15 a promise to pay a certain amount per week for placing an advertisement upon a curtain in a theater if such advertisement is in fact so placed;16 a promise to pay invalid assessments if a public improvement was completed, when such improvement was in fact completed, although the city did not agree to complete it;17 a promise to hire a hall at a certain rate, when so accepted by the promisee as to bind him to lease such hall;18 a promise by A to sell B's beer exclusively, as long, at least, as B supplies his beer, although B is not in terms bound to furnish such beer,19 are all illustrations of supplying mutuality; that is, of accepting by the doing of an act what was in legal effect an offer.

In some of these cases it may be doubted if the act which the courts treat as a consideration was really intended as such by the parties.20 A's promise to give to B one-half of the gold which B might locate on A's land, though without consideration at the outset, becomes a valid contract after B has sunk shafts and located gold at considerable expense.21 A promise to pay damages due to lack of fencing, made by a landlord who has permitted fences to be torn down wrongfully and who has refused to permit his tenants to rebuild them, in reliance on which such tenants did not rebuild such fences,22 and a promise of a railway company to carry logs at a certain rate, after a logging company has in reliance thereon given up its plan to haul logs across the railway at grade, and has changed its logging road at great expense,23 are both enforceable. If A gives B his note for services which B does not agree to perform, performance constitutes a consideration.24 Where A was to have half the oil which might be located on B's land by A's drilling, but A was not bound to drill, his drilling in pursuance of B's promise is a consideration, making a contract which equity will enforce specifically.25 A promise to pay a certain sum of money to a railroad when its road is completed to a certain place, is enforceable when the road is so completed.26 A promise by a railway to construct a side track by A's building, if A would move it to a specified point and repair and remodel it so as to make a warehouse, is accepted by A's moving, repairing and remodeling it, even though A made no prior promise so to do.27 A's promise to loan money to B in case B furnished satisfactory collateral, does not impose any liability on B, and it may be vague as to the collateral; but after A has accepted certain collateral from B as satisfactory, A is bound to perform.28

12 Underwood Typewriter Co. v. Century Realty Co., 220 Mo. 522, 119 S. W. 400.

13 Oconto Brewing Co. v. Cayouette, 138 Wis. 664, 120 N. W. 497. (A can not recover for beer furnished if he does not construct such depot.)

14Krausse v. Greenfield, 61 Or. 502, 123 Pac. 392.

15 Freudenthal v. Espey, 45 Colo. 488, 102 Pac. 280. (The employment here lasted about eight months.)

16Burnett v. Mam, 62 Or. 598, 125 Pac. 838.

17 Gerard v. Seattle, 73 Wash. 519, 132 Pac. 227.

18Buflington v. McNally, 192 Mass. 198, 78 N. E. 309.

19Feigenspan v. Nizolek, 71 N. J. Eq. 382, 65 Atl. 703.

20 See Sec. 522.

21Brown v. Bowman, 119 Ga. 153, 40 S. E. 410.

If, by the terms of the contract, the consideration is apportioned to each act as it is performed, the fact that B has performed a number of acts which he was not otherwise bound to perform, gives him a right of action for the performance of each of such acts against A, who has promised to pay such consideration, but it does not render A's promise to make such payments enforceable as to future services; and if A notifies B not to render further services, B can not recover damages from A.29

In some cases the original offer is so vague that the courts refused to enforce the promise, even after performance. A promise t6 waive future forfeitures for default in paying the purchase price under a contract to buy realty, if the vendee would remain on the land, plant an orchard, and cultivate the land, was held unenforceable, even if performed in part, since it did not impose upon the vendee the duty of remaining on such land, nor did it fix the time of payment.30 A promise by A and others, who raised grain, to pay to B one-half of the amount of any reduction in rates for transporting grain, irrespective of the cause of such reduction, whether by B's efforts or otherwise, B agreeing to begin a movement to secure a reduction in such rates, and to commence such proceedings and employ such attorneys at his own expense as he should think necessary, was held to be unenforceable, even after B had secured a hearing before the State Railroad Commission, as a result of which such freight rates had been reduced, on the theory that B's promise was so vague that it was impossible to determine whether he had performed.31 A promise by A to buy a certain amount of stock from B, if B bought a certain amount of stock from C, without any promise by B to sell such stock to A, was held unenforceable, although A bought such stock from C.32 While a contract may be so vague as to be unenforceable,33 most of the cases result in denying compensation under the contract to the party who has performed fully according to the most liberal construction of the contract in question.

22 Ensign v. Park, 69 Kan. 870, 77 Pac. 583.

23 Sultan Railway & Timber Co. v. Great Northern Railway Co., 58 Wash. 604, 109 Pac. 320 (hearing en banc denied, 109 Pac. 1020).

24 Miller v. McKenzie, 95 N. Y. 575, 47 Am. Rep. 85.

25 Spires v. Urbahn, 124 Cal. 110, 56

Pac. 794; Boyd v. Brown, 47 W. Va. 238, 34 S. E. 907.

26 Log Angeles Traction Co. v. Wil-shire, 135 Cal. 654, 67 Pac. 1086.

27 Thomas v. South Haven & E. R. Ry. Co., 138 Mich. 50, 100 N. W. 1009.

28 Murphy v. Hanna, 37 N. D. 156, L. R. A. 1918B, 135, 164 N. W. 32.

29 Grayling Lumber Co. v. Hemingway, 187 Ark. 327, 187 S. W. 327.