Aboard the Nellie, anchored in the River Thames near Gravesend, Charles Marlow tells his fellow sailors how he became captain of a river steamboat for an ivory trading company. As a child, Marlow had been fascinated by "the blank spaces" on maps, particularly by the biggest, which by the time he had grown up was no longer blank but turned into "a place of darkness". Yet there remained a big river, "resembling an immense snake uncoiled, with its head in the sea, its body at rest curving afar over a vast country and its tail lost in the depths of the land". The image of this river on the map fascinated Marlow "as a snake would a bird". Feeling as though "instead of going to the centre of a continent I were about to set off for the centre of the earth", Marlow takes passage on a French steamer bound for the African coast and then into the interior. After more than thirty days the ship anchors off the seat of government near the mouth of the big river. Marlow, with 200 mi (320 km) to go yet, takes passage on a little sea-going steamer captained by a Swede. He departs some 30 mi (48 km) up the river where his company's station is. Work on the railway is going on, involving removal of rocks with explosives. Marlow enters a narrow ravine to stroll in the shade under the trees, and finds himself in "the gloomy circle of some Inferno": the place is full of diseased Africans who worked on the railroad and now lay sick and gaunt, awaiting death. Marlow witnesses the scene "horror-struck."