This section is from the book "The Law Of Contracts", by William Herbert Page. Also available from Amazon: Commercial Contracts: A Practical Guide to Deals, Contracts, Agreements and Promises.
If A makes an offer to B concerning a given subject-matter, X; and B understands that A is making an offer concerning Y, and accepts the offer concerning Y, no contract exists.1 Where A, an auctioneer, offered a lot bearing one number, and B, understanding that it was a lot bearing a different number made a bid thereon which was accepted, no valid contract was made.2 So a mistake as to the tract of land agreed upon,3 or as to the location of a boundary line if "so material as to go to the essence of the contract,"4 prevents any valid contract from existing. Where the parties are mistaken as to the identity of the property contracted for, one of them can not have the contract, if in writing, reformed so as to express his understanding of what the property was.5 Mistake as to the identity of the subject-matter may affect a part of the property contracted for, and not the whole of it.6
19 Scott v. Coulson (1003), 2 Ch. 249.
20 Traders' Ins. Co. v. Aachen & M. F. Ins. Co., 160 Cal. 370, 8 L. R. A. (N.S.) 844, 89 Ac. 109.
1 England. Scriven v. Hindley (1913), 3 K. 8. 664; Raffles v. Wichelhaus, 2 Hurl. & C. 906.
Kaneaa. Interstate National Bank v. Ringo, 72 Kan. 116, 3 L. R. A. (N.S.) 1179, 83 Ac. 119; Haddon v. Neigh-barger, 9 Kan. App. 529, 58 Ac. 568.
Kentucky. McGowan v. Shearer, 176 Ky. 312, 195 S. W. 485.
Massachusetts. Spurr v. Benedict, 99 Mass. 463; Kyle v. Kavanaugh, 103 Mass. 356, 4 Am. Rep. 560.
Minnesota. Strong v. Lane, 66 Minn. 94, 68 N. W. 765.
Oklahoma. Kaiser v. Geis, 52 Okla. 604, 153 Ac. 148.
Rhode Island. Sheldon v. Capron, 3 R. I. 171.
Virginia. Lee v. Laprade, 106 Va. 594, 117 Am. St. Rep. 1021, 56 S. E. 719.
2 Scriven v. Hindley (1913), 3 K. B. 564; Sheldon v. Capron, 3 R. I. 171.
3 McGowan v. Shearer, 176 Ky. 312, 195 S. W. 485; Page v. Higgins, 150 Mass. 27, 5 L. R. A. 152, 22 N. E. 63.
4 Bigham v. Madison, 103 Tenn. 358, 47 L. R. A. 267, 52 S. W. 1074. If not material, such mistake does not avoid such contract; Murray v. Paquin, 173 Fed. 319.
5 Haddon v. Neighbarger, 9 Kan. App. 529, 58 Ac. 568.
6 Tyson v. Passmore, 2 Pa, 8t. 122, 44 Am. Dec. 181.
395 Mistake as to an Essential Element Sec. 263
Mistake as to the existence of part of the subject-matter may be made in transactions other than sales of realty. So where A by mistake handed B a ten-dollar gold piece of private coinage by mistake for a half dollar,7 or where A made a settlement with B for milk shipped by B to A, A assuming that the cans of milk contained five gallons each, when in fact they held less, some being spilled in transitu,8 or A agreed to deliver a certain amount of powder for B, by mistake as to the number of kegs and the weight of each keg,9 or A enters into a contract to buy stock in a corporation, under a mistake as to the identity of the corporation whose stock is being bought,10 such mistake avoids each of these contracts. If A signs as a joint maker with B and C, whose names are already affixed, the fact that B's name is a forgery prevents A's liability from attaching.11 A mistake as to the existence of certain injuries will prevent a release of damages arising out of known injuries from operating as a bar to an action for the unknown injuries, when discovered, even though the release may be drawn in general terms.12 Mistake as to the existence of a dam which backs up water so as to destroy a sewer, relieves from liability a contractor who has agreed to construct a dry-dock, and, as a part of such improvement, to rebuild a sewer in accordance with specifications furnished by the government.13