This is book 16 of the "Aubrey-Maturin" series.

This note contains spoilers for the book.

Undersea volcanos and tribal warfare on South-Sea islands. French idealists. Outright mutiny of a weird sort. And Stephen finally gets to South America and finds the time is very right for independence. Unfortunately things come apart, partly due to the French idealist, and he has to flee over high mountain passes into Chile.