 By the time Oxley had reached the Cumbung Swamp, he could advance no further due to the presence of 'impassable' marshland, eventually being forced to abandon the journey and to turn back.Oxley believed he had reached a marshy inland sea, concluding that the interior of Australia was 'uninhabitable' and unfit for settlement.Despite Oxley's bleak assessment of the Lachlan Valley, European settlement of the area began several years after the expedition.