Crescent

So with stun-sail piled on stun-sail, we sailed along, driving these leviathans before us; when, of a sudden, the voice of Tashtego was heard, loudly directing attention to something in our wake.

Corresponding to the crescent in our van, we beheld another in our rear. It seemed formed of detached white vapors, rising and falling something like the spouts of the whales; only they did not so completely come and go; for they constantly hovered, without finally disappearing.