Moby-Dick Chapter 118: The Quadrant Summary

It’s now the season for whale-hunting along the equator – the "Line" – and the crew are eager to obey Ahab’s orders to turn in that direction.
Ahab spends long periods sitting on deck, using his quadrant (a navigational instrument) to take measurements of the ship’s position.
He keeps comparing the exact location of the ship to Moby Dick’s likely position.
Eventually, Ahab gets frustrated, because no matter how precisely he measures the ship’s location, he’ll never really know where Moby Dick is.
He throws the quadrant down and tramples on it with his living foot and his bone leg.
Starbuck and Stubb watch Ahab, worried about the eventual fate of the voyage.