It is generally true that one who has led another to act in reasonable reliance on his representations of fact cannot afterwards in litigation between the two deny the truth of the representations, and some courts have sought to apply this principle to the formation of contracts, where, relying on a gratuitous promise, the promisee has suffered detriment. It is to be noticed, however, that such a case does not come within the ordinary definition of estoppel. If there is any representation of an existing fact, it is only that the promisor at the time of making the promise intends to fulfill it. As to such intention there is usually no misrepresentation and if there is, it is not that which has injured the promisee. In other words, he relies on a promise and not on a misstatement of fact; and the term ‘promissory’ estoppel or something equivalent should be used to make the distinction.' Williston on Contracts, Rev. Ed., Sec. 139, Vol. 1.