By the start of April 1834, had reached a stage in its survey voyage where minor repairs were needed to its keel and copper sheathing, so Captain Robert FitzRoy chose the river as a suitable place to lay the ship ashore. While this work was carried out, FitzRoy led an expedition upriver with aim of finding its source, distant in the Andes. Three boats set out on April 18, carrying twenty-five men, including FitzRoy and naturalist Charles Darwin. All involved took turn in teams dragging the boats up river for 16 days. Darwin took careful note of everything, including the terrain around the river the flora and fauna of the region, and the geology exposed as the river cut through the plains.