I found that passage (Amazon's "Search Inside" feature is handy - I look forward to the day when I can get all of these books in a searchable electronic format) and Stephen is writing in his diary, so the sand would be used to help dry the ink.
I was told before I posted the question here that no, he wasn't writing in the book, but perhaps I cloaked the query in confusing language, like asking if he was writing in the book.... :-)
My roommate thanks everyone for the answers, and promises he will read more carefully next time.
My question is this:
In Mauritius Command, Maturin is reading. When done, he dusts sand in the pages before closing the book.
Why does he dust the pages with sand?
I've checked the internet to see if there's any reference for this, but found none.
Thanks for answers in advance. :-)