1. Journey into the Unknown: Marlow portrays the river as a mysterious and dangerous entity, representing the unknown and unpredictable nature of the journey. He describes the river as "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."
2. Sense of Isolation: Marlow emphasizes the feeling of isolation and loneliness he experiences during the journey. He describes the river as "an immense wilderness, like a sea, and the primeval forest was the sky." The vastness and unfamiliarity of the landscape create a sense of remoteness and disorientation.
3. Hostile Environment: Marlow depicts the river and its surroundings as hostile and threatening. The dense jungle, impenetrable darkness, and treacherous currents pose constant dangers and challenges. He describes the river as "an enemy trying to get you, to break you, to maim you."
4. Encounter with Darkness: As the journey progresses, Marlow encounters increasingly disturbing and horrifying scenes, both physically and psychologically. The river becomes a metaphor for the darkness that lies within human hearts and the descent into savagery and madness. He witnesses the brutality and oppression of the European colonizers and the dehumanization of the indigenous people.
5. Loss of Identity: Marlow's journey up the river is also a journey of self-discovery and a search for identity. As he delves deeper into the heart of darkness, he faces his own inner demons and confronts his prejudices and preconceived notions. The journey becomes a transformative experience that challenges his moral compass and understanding of humanity.
Overall, Conrad's narrator describes going up the river as a journey fraught with danger, isolation, and confrontation with the darker aspects of human nature. The river itself becomes a symbol of the physical, psychological, and moral challenges that Marlow encounters during his voyage into the heart of Africa.