217. Notice to quit on a contingency.

A notice to quit must be clear and certain in its terms1. It is invalid if it is expressed so as to take effect on a contingency, such as a notice to quit given by the landlord if a breach of covenant is committed2, or a notice by the tenant to take effect when he can get another situation3. If, however, a definite notice to quit is given, it is not invalidated by the addition of words requiring, in a notice by the landlord, an increase4 or, in a notice by the tenant, a reduction, of rent, if the