Please teach me what "of which" means in the sentence.
People found a new source of entertainment while peering through Sir David Brewster's invetion, the kaleidoscope, the ever-changing patterns of which fascinated them.
I read that sentence in a book.
I guess I know what the sentence says, but I'm not sure what "of which" means, because I learn "of which" means "whose" but "whose" is mismatch this sentence.
so I guess "which" means kaleidoscope.
the ever-changing patterns of kaleidoscope fascinated them.
However, I've never seen that type of grammar before, so I don't have confidence.
Please teach me what "of which" means.