NavList:

I dug up some interesting insight into the subject from the writings of Charles Nordhoff (not to be confused with his similarly named grandson who later co-wrote Mutiny on the Bounty).  Nordhoff was a contemporary of Melville and had a diverse maritime career in the mid-19th century. He started out as a boy in the US Navy, went on to merchant ships, and finished up in the whaling industry. He  wrote an excellent trilogy of his experiences in each phase.

His merchant service included some time aboard a British vessel in the East Indies where much of the crew were Lascars.  On one voyage the threat of mutiny arose.

'But something more serious now claimed our attention. We had two white boys apprentices on board. These lads had learned the Hindostanee language and were much among the Lascar portion of the crew. The captain had instructed them already that they were to be cautious in their intercourse with these. He rathered favoured their intimacy with them as thereby he was more likely to learn of any plans of mutiny that might be hatching forward. We had not long been on half allowance when one of the boys informed us that the Lascars had asked him apparently by chance but evidently with a purpose whether he understood navigation. The boy could navigate the captain having taught him. But he had the good sense to answer in the negative. His interrogators were evidently much disappointed. The other boy was also questioned but with a similar result. By a little management the lads obtained sufficient information of their plans to show us that they had intended could either one of the boys navigate to rise and murder all the Europeans except that boy. They intended to preserve him and force him to take the vessel when a breeze came into the neighbourhood of some port in the Bay of Bengal where they would set fire to the barque to conceal their crime and go ashore in the boats...'

Aboard whaling ships, Nordhoff found that the chief threat was desertion.  Whaling was so mind-numbingly boring that a large portion of the crew would try to desert when given the chance in a foreign port.  Melville was a good example, deserting the Acushnet mid-voyage in the central Pacific.  Nordhoff found his own escape in a stolen whale boat while off Madagascar, along with five other  shipmates,

'Two of our number could navigate and we had with us a quadrant, a Bowditch, and a small chart of the coast of Madagascar by the help of which we trusted to be able to find our way over the deep. We elected Long Tom Coffin ... our chief and then divided ourselves off into watches holding the helmsman for the time being responsible for a correct reckoning of the course and distance made during his trick and putting upon Long Tom the labor of keeping a regular log...'

They used dead reckoning and latitude observations to make their way to Mozambique.

Don Seltzer