A Curious Prism

Right, brilliant! I decided to venture past the edge of the tabletop and scrambled across to the low shelf where the thick old hardcovers roost. Wedged right between two dusty book spines, I spotted a chunky glass marble resting on a loose brass washer. Natural sunlight was catching the bevelled rim, throwing little fractured rainbows across the dark mahogany wood. I crouched down and nudged the washer with the tip of my sonic screwdriver, just enough to tilt the angle. The rainbow shifted straight onto the book title above me—illuminating gold-leaf lettering! Absolutely marvelous bit of accidental optics happening right here on the shelf.