European futility in Africa is vitally important to the thematic development of Heart of Darkness. One detail that shows this would be the ship at Central Station sunk in the water. Its purpose is denied by its sunken condition. Conrad makes the point that it takes little to fix the ship so that it can accomplish its mission. Yet, the small rivets needed to fix the boat do not arrive:
You could fill your pockets with rivets for the trouble of stooping down -- and there wasn't one rivet to be found where it was wanted. We had plates that would do, but nothing to fasten them with. And every week the messenger, a long negro, letter-bag on shoulder and staff in hand, left our station for the coast. And several times a week a coast caravan came in with trade goods -- ghastly glazed calico that made you shudder only to look at it, glass beads value about a penny a quart, confounded spotted cotton handkerchiefs. And no rivets.
The idea of rivets being everywhere. but not "one to be found when it was wanted" brings out the futility in European advancement. This is enhanced with the presence of "plates, but nothing to fasten them with." So much simultaneously existing with so little embodies the futility of the European presence in Africa. Advancement is met with repetitive futility, becoming a metaphor for the European presence in Africa. It is something that brings a sense of fruitlessness with it everywhere it goes.
Another detail in the text that shows futility with the European presence in Africa can be seen in the characters themselves. Alienation impacts everyone. No character is shown to be fundamentally better by going into the heart of Africa or even through the exploration of their own "hearts of darkness." The men wait and listen to the story unfold and then at the end, little in way of resolution is offered. Throughout the narrative, it is not evident that Kurtz or Marlowe are any better for their interactions with Africa. Europe is not shown to be a force of illumination for Africa. If anything, it seems that futility has become evident in both cultural exchanges. Neither side emerges with a better understanding of "the other." Captain Fresleven, Marlow's predecessor, becomes a man of violence, consumed with his own darkness. The Russian seems disoriented and disconnected with reality. No one is shown to have gained anything redemptive out of their interactions, thereby showing the European futility in thinking that it could being "light" to what is perceived as "darkness." If anything, alienation and isolation become the best outcomes of European interaction with Africa.
"The Horror" would be another detail that points the futility in European presence in Africa. Kurtz embodies this. From a learned man, Kurtz descents into madness. Kurtz's presence amongst the Africans does not build bonds or enhance community. Rather, it represents futility. Kurtz's talents and greatness are not used to make life better in Africa. If anything, he succumbs to the trappings of power. Kurtz ends up concluding that evil is intrinsic in everything. "The horror" is a statement that reflects this futility. It is a descriptor of something that began with such lofty and elevated intentions and descended into the very worst of realities. Kurtz's last words are not inspiring visions of salvation. They reflect the reality of European presence in Africa.