This term is applied to those rights which are cast upon a party by the law, without any act of his own; as, the right to an estate of one who dies intestate, is cast upon the heir at law, by operation of law; when a lessee for life enfeoffs him in reversion, or when the lessee and lessor join in a feoffment, or when a lessee for life or years accepts a new lease or demise from the lessor, there is a surrender of the first lease by operation of law.