In Ch. 42, I was struck by the two mentions of a Grecian temple, and Marianne's wish to walk there by twilight.

I was searching around online a bit, and it seems that these landscape design features were more of the 18th century, while the picturesque movement in the early 19th century (of which Marianne is a fan) wanted to get rid of the formerly populsar calm tranquil lawns, lakes and Grecian temples in favour of ruins and romantic wildness with jagged irregular shapes.

I found it curious that the Palmers, first of all, who seem to want to spend their money on whatever is new and fashionable would have in the pleasure-grounds of their 'spacious, modern-built' house a design feature that was on its way out of style by that time and also that Marianne who is such an advocate of the picturesque would seek out something that was rather the opposite of that. Was she, despite what I said in the other post on violence a bit down the board, actually being drawn to something more soothing, despite her wish to rejoice in her agony?

I also found this poem by Cowper, that I could imagine Marianne reciting to herself as she walked (In between outbursts of "Willoughby! Willoughby!")

 Oh happy shades--to me unblest!
Friendly to peace, but not to me!
How ill the scene that offers rest,
And heart that cannot rest, agree!

This glassy stream, that spreading pine,
Those alders quiv'ring to the breeze,
Might sooth a soul less hurt than mine,
And please, if any thing could please.

But fix'd unalterable care
Foregoes not what she feels within,
Shows the same sadness ev'rywhere,
And slights the season and the scene.

For all that pleas'd in wood or lawn,
While peace possess'd these silent bow'rs,
Her animating smile withdrawn,
Has lost its beauties and its pow'rs.

The saint or moralist should tread
This moss-grown alley, musing, slow;
They seek, like me, the secret shade,
But not, like me, to nourish woe!

Me fruitful scenes and prospects waste
Alike admonish not to roam;
These tell me of enjoyments past,
And those of sorrows yet to come.

The notes in my book of Cowper's poetry said that Cowper, who did suffer a breakdown himself the same year he wrote this poem (1773), usually found peace and tranquility in seclusion, but not in the state he was in when he wrote this poem.

Right at the end of the chapter, we read that Marianne had two delightful walks "not merely on the dry gravel of the shrubbery, but all over the grounds, and especially in the most distant parts of them, where there was something more of wildness than in the rest, where the trees were the oldest..."

That made me think that Marianne, at this point, is kind of torn between these two ideas--wishing, perhaps, to find some peace in seclusion, yet still wanting (and believing she ought?) to 'nourish her woe' and seek out the wildness.