Sentence:  Quite unconscious of the demonstrations of their amorous neighbour, or their effects upon the susceptible bosom of her mama, Kate Nickleby had, by this time begun to enjoy a settled feeling of tranquillity and happiness, to which, even in occasional and <WSD>transitory</WSD> glimpses, she had long been a stranger. 
Meaning of the word marked with <WSD> tags:  Lasting only a short time; temporary.