Darkness is a major theme of the story and the river is one of the first places we discover this darkness.
The fact that the woman is enshrouded in darkness with only insufficient torchlight to guide her says a lot about the nature of our society. Conrad is trying to show that the little area of the Congo of Africa is symbolic of how things are run in the much larger English society.
When Marlow arrives at the Central Station he is told that his boat has been sunk and it will take a while before the parts arrive to repair it.
It almost seems as if the jungle itself did not want their company.
When Marlow states, "I had got a heavenly mission to civilize you," he expresses his good intentions to help the Africans progress and advance. Conrad uses the depths of the Congo to show how morals, restraint, and conscience escape from man when he is taken out of civilization Although Heart of Darkness is a famous literature that was criticized by Chinua Achebe and each of their work represents different point of views during similar time of history, both literatures have a similarity that they operate iconography in relation to race, class and identity with their own interpretations of symbols and icons This may be because Heart of Darkness was more an inner journey than a journey between places.
Charlie Marlow the protagonist and central character spoke fondly of the large blank map of Africa when he was a boy.