After waiting for Darwin, "Beagle" sailed on 11 November to survey the Chonos Archipelago. From here, they saw the eruption of the volcano Osorno in the Andes. They sailed north, and Darwin wondered about the fossils he had found. The giant "Mastodon"s and "Megatherium"s were extinct, but he had found no geological signs of a "diluvial debacle" or of the changed circumstances that, in Lyell's view, led to species no longer being adapted to the position they were created to fit. He agreed with Lyell's idea of "the gradual birth & death of species", but, unlike Lyell, Darwin was willing to believe Giovanni Battista Brocchi's idea that extinct species had somehow aged and died out.