Mistake concerning collateral matters may sometimes, however, afford ground for relief. Where a mistake as to the quantity, quality, or characteristics of the subject of a bargain is due to a mutual mistake regarding some means or measure which the parties took for fixing the quantity, quality, or value of the performance rendered by one party, it seems clear that there may be rescission.87 In some cases, moreover, the difference between the real and supposed quality or nature of the thing is so extreme that without any preliminary error as to the means of determining these matters, a contract based on a mutual mistake in regard to quality or characteristics has been rightly held voidable. As an illustration of this it may be supposed that a bargain is made for the sale of a specific bar of metal understood to contain a certain proportion of silver. Through some mistake the understanding of the parties may be erroneous, and the bar may be base metal instead of gold or silver as supposed.88
It will be noticed that there is an actual sale of the bar in question. There was a clear expression of assent to the sale of that particular bar. The case, therefore, is one of rescission of a sale on equitable grounds. As in most cases where chattels are involved, the remedy is at law." Similarly, where a watch was sold on the assumption that it was gold, when in fact it was base metal, rescission was permitted.40 The same result follows if the subject-matter is essentially better instead of essen-tially worse than supposed. Where parties bargained for the sale of a cow under the mutual impression that the cow was barren, the seller was held not bound to deliver the animal when it was discovered to be a breeder.41 The same principle is involved in some cases of sales of real estate which did not have the timber,42 or ore 43 which the parties supposed, and which formed the main inducement to the bargain. So where land was leased with the expectation that a wooden building could lawfully be erected thereon, and unknown to the parties, two days before, a municipal ordinance forbade this, the lease was rescinded.44 And where water power was leased for the pin-pose of grinding pulp, an unknown limitation in the lessor's right, precluding such use, was held to bar recovery of rent.45 Another illustration of the same principle is found where parties enter into a contract to sell on the assumption that the goods to which the bargain relates are then in good condition. This matter is covered by special provisions in the Sales Act.46 Where relief has been granted because a bid has been given under a miscalculation 47 the mistake is not only unilateral but is collateral. The bidder knows the sum of money he bids and the only mistake which he makes relates to its quality or characteristic - its equality to the total of certain items the bidder intended to include. It may be urged that the bidder meant to bid this total, and that the sum he did bid was a different thing. But he was not asked to add up items or bid the total of items, he was asked for a bid in gross and made such a bid.48 On the other hand, a mistake as to the book value of bank stock due to the fraudulent manipulation of the books by a bank clerk, so that the book value appeared to be more than twice what it was in reality, was held no ground for rescission.49
36 Harris v. Loyd, 5 M. & W. 432; Aiken v. Short, 1 H. & N. 210; Cleveland Cliffs Iron Co. v. East Itasca, etc., Co., 146 Fed. 232, 237-238, 76 C. C. A. 606; Brooks v. Hall, 36 Kans. 697, 14 Pac. 236; First Nat. Bank v. Burkham, 32 Mich. 328; Langevin v. St. Paul, 49 Minn. 189, 196, 51 N. W. 817, 15 L. R. A. 766; Southwick v. First Nat. Bank, 84 N. Y. 420, 434; Youmans v. Edger-ton, 91 N. Y. 403, 411. And see Holt v. Thomas, 105 Cal. 273, 38 Pac. 891.
37 E, g., where a survey (McMahan v. Terkhorn, (Ind. App. 1917), 116 N. E. 327; Gilroy v. Alis, 22 la. 174; Coon v. Smith, 29 N. Y. 392; Jenks v. Fritz, 7 W. & S. 201, 42 Am. Dec. 227); appraisement (Freeman v. Jeffries, L. R. 4 Ex. 189), inventory (Sheffield v. Hamlin, 26 Hun, 237), or assay (Cox v. Prentice, 3 M. & S. 344), is made the basis of the bargain. See also Nordyke, etc., Co. v. Kehlor, 155 Mo. 643, 56 S. W. 287, 78 Am. St. Rep. 600; Wheadon v. Olds, 20 Wend. 174. Cf. Buffalo v. O'Mailey, 61 Wis. 255, 20 N. W. 913, 50 Am. Rep. 137.
38The supposition is based on Cox v. Prentice, 3 M. A S. 344. In that case there was an error in the assay and the case therefore belongs with those in the preceding note; but at least if the difference in value was extreme, it may be supposed that even though there had been no assay, relief would have been given. See also Terry v. Bissell, 26 Conn. 23, 32.
39See supra, Sec.Sec. 1369 et seq.
40 Sparling v. Marks, 86 Ill. 125.
41 Sherwood v. Walker, 66 Mich. 568, 33 N. W. 019 (see also Cotter v. Luckie,  N. Zeal. L. R. 811, stated, supra, Sec.1569, n. 33). Cf. Wood v. Boynton, 64 Wis. 265, 25 N. W. 42, 54 Am. Rep. 610. Neither in England nor in Illinois or Michigan (prior to the enactment of the Sales Act) was rescission allowed merely for breach of warranty (see supra, Sec. 1462). Therefore, the decisions referred to in this and the preceding note must be rested on the ground suggested in the text. If A buys from B, and pays for a mass of oats at a fixed sum per bushel, the quantity being estimated by the quantity of a portion of the mass which has been measured, which both suppose to contain 500 bushels, though in fact it contains but 500 half-bushels, A can recover from B for the excess of the estimated over the real quantity. Wheadon v. Olds, 20 Wend. 174. And see Devine v. Edwards, 87 I11. 177. So a contract for letting seats from which to see an expected coronation procession was held unenforceable because unknown to the parties at the time they entered into the agreement the plan of a procession had been abandoned. Clark v. Lindsay, 88 L. T. Rep. 198; Griffith v. Brymer, 19 T. L. Rep. 434. See also German Civil Code, Sec. 119, quoted supra, Sec. 1546, n, 37.
41 Thwing v. Hall & Ducey Lumber Co., 40 Minn. 184,41 N. W. 815; Blygh v. Samson, 137 Pa. 368, 20 Atl. 996.
43 Dale v.Roosevelt, 5 Johns. Ch. 174.
44 Hannah v. Steinman, 159 Cal. 142, 112 Pac. 1094. See also Williams p. Miller, 68 Cal. 290, 9 Pac. 166, where an agreement to pasture cattle was based on the mistaken assumption that adequate pasturage existed on the tract in question.
45Bedell v. Wilder, 65 Vt. 406, 26 Atl. 589, 36 Am. St. Rep. 871. But see Albany Heights Realty Co. v.