A promise not under seal is unenforceable unless supported by a valuable consideration.1 No remedy for such promise is given, either at law or equity, and accordingly specific promise is denied.' If a contract is made by mutual executory promises, the same promise which forms the consideration forms also the acceptance of the other promise. In cases of this sort, therefore, offer and acceptance and consideration happen to consist in one and the same act. They are classed by many courts as cases in which specific performance is denied because of a want of mutuality.