18. Examples of mistake as to subject matter relieving mistaken party from liability.

In the case of a contract for the sale of a cargo supposed to exist and to be capable of transfer, but which in fact had been sold and delivered to others before the contract was made, it was held that the vendor could not recover the price of the cargo1. Similarly, when an annuity is sold after, and in ignorance of the fact that, it has ceased to exist, the purchase money may be recovered as having been paid without consideration2; and it is likewise if parties to litigation over certain chattels enter into a consent order on