Somewhat analogous to the surrender of a supposed claim as consideration for a promise, is the assignment of a supposed right of another kind. Certainly if the parties confessedly bargain for the assignment of such right as the grantee may have, be it small or great, or none at all, the assignment in fact is sufficient consideration for a promise though it turns out that there is no right transferred.1 The only possible exception to such a rule is, that if no reasonable person could suppose the assigned chance was of any value, it might then be insufficient consideration. But even in such a case the execution of a quitclaim deed or other desired paper would support a promise.2 If an assignment of a supposed right is made on the justifiable assumption by the assignee that he is to receive not merely such possible right as the assignor may have, but an actual right, the assignee's defence to any promise made by him in consideration of the assignment, if it turns out that no right was conveyed thereby, seems to be mistake or failure of consideration rather than lack of consideration.3 Questions of this sort have not infrequently arisen where patentees have either sold patents or licensed others to use the patented invention in return for a promise of payment. In some cases it has been laid down broadly that there is no consideration for a promise to pay money in return for a patent, which is for any reason void.4 But it cannot be admitted that a patent which is void, though not known to be-so, may not be sufficient consideration for a promise, if the bargain was for the actual patent with such right as it might carry-much or little or none at all; and "perhaps from a disinclination to go so far as the American courts in holding that a vendor impliedly warrants his title to a chattel sold while in his possession, and perhaps in part on account of the practice there in relation to issuing patents, the courts in England hold that one who purchases a patent, or rights under a patent, in the absence of fraud and of express stipulation, must be presumed to look to the existence of the patent as a document which prima facie gives a right, rather than to the facts behind the patent upon which its validity depends."5 In the United States, it seems clear that presumptively the bargain though technically for a specific patent must be understood to contemplate that the assigned patent will confer a valid right upon the assignee. Therefore though an assignment of a patent be strictly what was requested, yet if it does not give the assignee the exclusive privilege contemplated, there is a failure of consideration, which will be a defence to an action for the promised price 6 even though the promise, being under seal, needed no consideration.7 In regard to licenses given in good faith under an invalid patent, the distinction has been taken that where the patent is on its face valid and the licensee receives the benefit of a monopoly, he cannot set up the invalidity of the patent.8 But if the licensee has not received the exclusive rights which would have been his had the patent been valid, he is not bound to pay the agreed license fees.9 The propriety of this distinction is obvious if it is recognized that failure of consideration is the basis of decision; but if there were originally no consideration for the licensee's promise, the licensor could not recover the promised price, whatever benefit in fact might have been derived by the licensee. A license under an invalid copyright is treated in the same way as a license under an invalid patent.10

1 Sykes v. Chadwick, 18 Wall. 141, 21 L. Ed. 824; Cobb v. Heron, 180 111. 49, 54 N. E. 189; Weatherford v. Boul-ware, 102 Ky. 466, 43 8. W. 729; Palmer v. Gufflow, 224 Mass. 1, 112 N. E. 493. See also Begbie v. Phosphate Sewage Co., L. R. 10 Q. B. 491, 1 Q. B. D. 679.

2See supra, Sec. 116.

3 See infra, Sec. 814.

4Harlow v. Putnam, 124 Mass. 553; Gloucester, etc., Co. v. Russia Cement Co., 154 Mass. 92, 95, 27 N. E. 1005, 12 L. R. A. 563, 26 Am. St. Rep. 214; Joliffe v. Collins, 21 Mo. 338; Rowe v. Blanchard, 18 Wis. 441, 86 Am. Dec. 783; 3 Robinson on Patents, Sec.1230.

5 Chemical Electric Light, etc., Co. v. Howard, 148 Mass. 352, 359, 20 N. E. 92,2 L. R, A. 168, citing-Hall v. Con-der, 2 C. B. (N. 8.) 22, 53; Smith v. Neale, 2 C. B. (N. S.) 67; Noton v. Brooks, 7 H. & N. 499; Trotman v. Wood, 16 C. B. (N. S.) 479; Lawea v. Purser, 6 E. & B. 930; Adie v. Clark, Ch. D. 134.

6 Nye v. Raymond, 16 111. 153; Mo-Clure v. Jeffrey, 8 Ind. 79, 82; Lester p. Palmer, 4 Allen, 145; Harlow v. Putnam, 124 Mass. 553; Keith v. Hobbe, 69 Mo. 84; Dunbar v. Harden, 13 N. H. 311, 317; Cross v. Huntly, 13 Wend. 385; Mareton v. Swett, 66 N. Y. 206, 212, 23 Am. Rep. 43; Herzog v. Hey-man, 151 N. Y. 587, 45 N. E. 1127; Darst v. Broekway, 11 Ohio, 462, 471; Herman v. Gray, 79 Wis. 182,48 N. W. 113. And a promise to pay the price of a machine is subject to a similar defence if the right to use the machine can be effectively disputed by a third person. Pratt v. Paris Gas Light Co., 155 111. 531,40 N. E. 1032. But where the seller of a patent was himself an assignee, he was allowed to recover the agreed price in Johnson v. Willimantic linen Co., 33 Conn. 436.

7Hayne v. Maltby, 3 T. R. 438; Nye v. Raymond, 16 111. 153.

8 Kinsman v. Parkhurst, 18 How. 289, 15 L. Ed. 385; Wilder v. Adams, 2 Woodb. &. M. 329; McKay v. Jackman, 17 Fed. 641; Millligan v. Lallance, etc., Mfg. Co., 21 Fed. 570; Covell v. Bostwick, 39 Fed. 421; Bartlett v. Holbrook, 1 Gray, 114; Marston p. Swett, 66 N. Y. 206, 23 Am. Rep. 43; Skinner v. Wood Co., 140 N. Y. 217, 35 N. E. 491, 37 Am. St. Rep. 540; Hyatt v. Dale Mfg. Co., 106 N. Y. 651, 12 N. E. 705; Davis v. Gray, 17 Oh.