At the Department of Mysteries

They crept forward, glancing behind them as they went on down the long alleys of shelves, the further ends of which were in near-total darkness. Tiny, yellowing labels had been stuck beneath each glass orb on the shelves. Some of them had a weird, liquid glow; others were as dull and dark within as blown light bulbs.
(OotP, UK edition, p. 686)