There was something about it that made me uneasy.

It looked old-fashioned and neglected, but, notwithstanding its ordinary seeming, the eagle, perched with outstretched wings on the top, appeared threatful.
"As a mirror," said the librarian, "it has grown dingy with age; but that is no matter: its clearness depends on the light." "Light!" I rejoined; "there is no light here!" He did not answer me, but began to pull at a little chain on the opposite wall.

I heard a creaking: the top of the chamber was turning slowly round.

He ceased pulling, looked at his watch, and began to pull again.
"We arrive almost to the moment!" he said; "it is on the very stroke of noon!" The top went creaking and revolving for a minute or so.

Then he pulled two other chains, now this, now that, and returned to the first.