The narrator observes, "hunters for gold or pursuers of fame, they all had gone out on that stream bearing the sward, and often the torch..." What do the sword and the flame symbolize, and what might they have to do with a story about africa?

I think this has to do with the violence and disregard colonial explorers had for the continent and her indigenous people.

Oh you wanted to specify sword and flame. I think sword symbolizes the obvious. It is to take control by force. The torch would burn the existing cultural and physical infrastructure down only to replace it with an oppressive tyranny bent on raping the continent for her resources and enslaving the indigenous populations.