How we cite our quotes: Citations follow this format: (Book.Chapter.Paragraph)
Quote #1
The imagination of the observer clung by preference to that vanished, solitary figure, as to something more interesting, more important, more likely to have a history worth knowing than these new-comers, and unconsciously regarded them as intruders. (1.2.46)
Diggory thinks this about Eustacia, but the novel as a whole seems to believe it too – the idea that the "solitary figure" has a more interesting story than the community. And this book definitely focuses on a series of solitary figures (though it doesn't ignore the community and human connections). This idea of a "solitary figure" is a very Romantic idea as well; Naturalist thinking is more likely to describe an isolated figure, which has a more negative connotation, or meaning.
Quote #2
That five minutes of overhearing furnished Eustacia with visions enough to fill the whole blank afternoon. [...] She could never have believed in the morning that her colourless inner world would before night become as animated as water under a microscope, and that without the arrival of a single visitor. (2.9.29)
We get a very strong sense of how isolated Eustacia is, and of how much she lives inside her own head. The mention of the microscope is also unusual; this book doesn't otherwise use many scientific or technological comparisons. This might just be a random comparison, but it draws attention to how little technology of any sort features in the novel.
Quote #3
Yeobright reached the empty house about mid-day. It was almost as lonely as that of Eustacia's grandfather, but the fact that it stood near a heath was disguised by a belt of firs which almost encircled the premises. (3.6.6)
The detail about the trees "disguising" the heath is significant here. When they first arrive at their new home, Clym and Eustacia live in a fantasy land that's practically a bubble, and Eustacia ignores the fact that they still live on the heath in favor of dreaming about Paris.
Quote #4
It was the room in which, six months earlier, the merry Christmas party had met. [...] The only living thing that entered now was a sparrow. [...] This roused the lonely sitter, who got up, released the bird, and went to the door. (3.7.1)
This entire chapter is a painful portrait of loneliness. In this scene, we get a sense of how Mrs. Yeobright is haunted by past memories in her lonely house. It's also worth noting the bird in this scene – you can read more about "Bird" imagery and symbolism in the "Symbols, Imagery, Allegory" section.
Quote #5
A domestic drama, for which the preparations were now being made a mile or two off, was but little less vividly present to her eyes than if enacted before her. She tried to dismiss the vision, and walked about the garden-plot, but her eyes ever and anon sought out the direction of the parish church [...]. (3.7.2)
There's a dual sense of isolation and connection going on here. It's like Mrs. Yeobright's mind is completely at the church where her son is getting married, even though her body is still at her lonely home. The detail about how her eyes keep "seeking" out the church is key here.
Quote #6
The absolute solitude in which they lived intensified their reciprocal thoughts; yet some might have said that it had the disadvantage of consuming their mutual affections at a fearfully prodigal rate. (4.1.2)
Though solitude and isolation are often portrayed negatively, we see here that isolation can also be romantic and happy. But, of course, this passage doesn't end on a happy note. Instead, we get an ominous warning about how Clym and Eustacia are going to (literally) burn themselves out at the rate they are going.
Quote #7
As day after day passed by, and he got no better, her mind ran more and more in this mournful groove, and she would go away from him into the garden and weep despairing tears. (4.2.37)
This image of Eustacia parallels the earlier image of Mrs. Yeobright wandering around in her lonely garden, wondering about her son. The distinction here is that Eustacia is focused internally, with her mind stuck in a "mournful" rut, while Mrs. Yeobright was focused externally, imagining her son.
Quote #8
In front of her a colony of ants had established a thoroughfare across the way, where they toiled a never-ending and heavy-laden throng. To look down upon them was like observing a city street from the top of a tower. (4.6.107)
The image here gives us a strong sense of isolation – it's literally lonely at the top for Mrs. Yeobright as she looks down on the ant colony. The comparison of this colony of ants to a city is very interesting, too. Is Hardy saying that cities are as inconsequential as a hill of ants or that ants (and nature) are as important as, say, Paris? Maybe a bit of both.
Quote #9
"Two months and a half, Thomasin, the last of her life, did my poor mother live alone, distracted and mourning because of me; yet she was unvisited by me, though I was living only six miles off. Two and a half months – seventy-five days did the sun rise and set upon her in that deserted state which a dog didn't deserve!" (5.1.31)
The link of time and loneliness makes this passage even sadder and is a good rhetorical trick that Clym uses to hammer his point home to Thomasin. We get a strong sense here of how Mrs. Yeobright was isolated and distanced from others – in terms of physical distance (miles), in terms of time (months), and in terms of endless, repeated days where the sun kept rising and setting. The final comparison of her state to that of an abused "dog" is quite jarring.
Quote #10
"I – I –" she began, and then burst into quivering sobs, shaken to the very heart by the unexpected voice of pity – a sentiment whose existence in relation to herself she had almost forgotten. (5.5.61)
Eustacia's inability to even speak clearly further emphasizes her isolation, and the detail about how she has "forgotten" kindness creates a lot of sympathy for her.