I agree with you both about Lizzy--she seems intrigued by Randolph's interest in the supernatural. As to why, my impression is that the novelty of the idea makes her want to hear more. Lizzy has a lively mind but she's had precious few opportunities to use it outside a very limited sphere. Also, she's established as being one who enjoys the study of people's character and here's a wealth of extraordinary ideas for her to ponder.

I don't think she'd ever in a million years actually participate, but I do think she considers it a harmless diversion. In fact, I venture to say that she trusts that Randolph's motivations are similar to her own--a purely academic interest. Unfortunately, my own feelings on the subject run in exactly the opposite direction. These two Americans are up to something and I cannot think it is good.

Darcy, on the other hand, has not been out and about in the world more than his wife has been. He's also infinitely more practical and his ideas, I think, are more fixed. In a nutshell, he knows what he knows and probably figures that he what he knows is the absolute truth.

As for the solstice, I did the teeniest bit of digging and found out a couple of interesting things.

First of all, the word solstice means, "standing-still sun". The first thing I thought of when I saw this was those sun-shaped wedding bands. Coincidence or something of significance? What do you think?

According to the articles I found, the celebration of the winter solstice goes back to ancient times. The Ancient Greeks "celebrated" with human sacrifice. The Druids believed the WS marked the time of year when the Sun God went into the underworld to seek out the mysteries of life and death. (There's the sun again!)