How was the atmosphere in the story?

There is much atmosphere to this story. Most of it has a mournful obsessively dark feeling to it. There is a sense of otherness about the Congo and its inhabitance that Marlow is not a part of. At times it is chaotic and other times it foreboding.

"The smell of mud, of primeval mud, by Jove! was in my nostrils, the high stillness of primeval forest was before my eyes; there were shiny patches on the black creek. The moon had spread over everything a thin layer of silver -- over the rank grass, over the mud, upon the wall of matted vegetation standing higher than the wall of a temple, over the great river I could see through a sombre gap glittering, glittering, as it flowed broadly by without a murmur. All this was great, expectant, mute, while the man jabbered about himself."