Discrepancies
The Pequod is initially described as having by a tiller made from a whale's lower jaw, yet in one instance the helm is described as having "spokes", which refers to a wheel. (Interestingly, both of the movie versions retain this anomaly, showing both steering elements aboard the same ship).
During the most violent shocks of the Typhoon, the man at the Pequod's jaw-bone tiller had several times been reelingly hurled to the deck by its spasmodic motions, even though preventer tackles had been attached to it - for they were slack - because some play to the tiller was indispensable. —Moby-Dick, Ch. 123 "Clear away the boats! Luff!" cried Ahab. And obeying his own order, he dashed the helm down before the helmsman could handle the spokes. —Moby-Dick, Ch. 61 ...every day when Ahab, coming from his cabin, cast his eyes aloft, the vigilant helmsman would ostentatiously handle his spokes... —Moby-Dick, Ch. 118Read more about this topic: Pequod (Moby-Dick)