This episode, in chapter 16, is something that I am still mentally grappling. He nearly brought the Marble Lady to life, and even without that, he made her visible. He was in the presence of his Lady, and how my heart wished that he would finally find her, rescue her, bring her to life. This is the catharsis that both the protagonist and I are looking for.
But it doesn't happen. This introduces the second of the protagonist's depressions.
The main question I'm grappling with is why the protagonist should not touch her, why is it that he should have sung to her? When you consider the Marble Lady to be figurative for the artistic ideal, what would it mean to touch her?
I've spent an hour now thinking about this question, and the closest I have to an answer is this: it presents a dichotomy between force and inspiration. That's all I got.
In terms of the story line, this marks the protagonist's abrupt departure from the Fairy Palace. He does not return, nor will he ever meet the Fairy Queen, which was a bit of an anti-climax to me, but most assuredly does MacDonald make up for it later.