Lat Thlngs in-tervening; that ls, things done by one of the partles to a contract, ln the falth of Its va-lldity, and with the assent of the other par-ty, and whlch have so affected his situation that the other will not be allowed to repudi-ate his obligation, although originally lt was imperfect, and he might have renounced it. 1 Bell, Comm. 328, 329