Mary refrained from saying what she felt, that there could not be two persons in existence whose characters and manners were less accordant: time would discover it to him; but she could not help _this_ reflection on the Admiral. 
Mary refrained from saying that two people could not be less alike; but she could not help remarking, "Henry, if I supposed the next Mrs. Crawford were to be treated like my poor aunt, the Admiral's wife, I would prevent the marriage; but I know you. 