In Chapter 7, Dickens's third-person omniscient narrator uses anthropomorphism to imply that the Dedlocks are less happy than the animals who live at their house, as remembering the past is only safe for the dumb animals of the estate:
There may be some motions of fancy among the lower animals at Chesney Wold. [...] So, the mastiff, dozing in his kennel [...] may think of the hot sunshine [...] So the rabbits with their self-betraying tails, frisking in and out of holes at roots of trees, may be lively with ideas of the breezy days when their ears are blown about [...]
Be this as it may, there is not much fancy otherwise stirring at Chesney Wold. If there be a little at any odd moment, it goes, like a little noise in that old echoing place, a long way, and usually leads off to ghosts and mystery.
Dickens goes through a taxonomy of the estate's domestic and wild animals, having them think through happier times as they gently dream. Although it's raining and miserable, they have "motions of fancy" which allow them to distance themselves from the "wet weather" of Lincolnshire and the "old echoing" of Chesney Wold. The sensory language Dickens uses here to describe the animals' memories is bucolic and charming, as visual images of "lively" rabbits "frisking" and physical sensations of "hot sunshine" are described.
When the animals here engage in "fancy," Dickens means that they are remembering or daydreaming about the past. For humans, though, there is "not much fancy" in Chesney Wold. Daydreaming of the past only "leads off to ghosts and misery." The easy access to past happiness the animals enjoy contrasts sharply with the danger of recalling the past for Lady Dedlock, the mistress of the house. Although the Dedlocks have money, their past eventually destroys all the benefits of their privilege.
When the wealthy Lady Dedlock is reminded of her past transgressions and her closely guarded secrets, she is horribly ashamed. Engaging in the "fancy" of remembering previous events only "leads off to ghosts" and makes her miserable. These animals, however, even though they have nothing, can innocently enjoy memories and dreams which allow them to remember happier times. Dickens spends a long time describing these detailed "fancies" of the animals at Chesney Wold: the exhaustive descriptions extend for an entire page. When Dickens makes it clear that money can't protect Lady Dedlock from the "misery" that "hunts" her in Chapter 55, her situation seems even more unhappy and her privilege even more useless. Even the dogs who sleep on her floors are happier than she is.
