This chapter, which on the surface is a mere scene-setting in lovely language, is actually a densely-layered introduction to the symbolism of the novel. Nostromo is a highly symbolic and imagistic novel, and its themes can only be fully understood by being able to 'read' its symbolism. Although the deeper meaning of the imagery in this chapter builds gradually over the course of the novel, and wouldn't be apparent on a first reading, my notes here will call attention to it.
There is also meaning in the very fact that Conrad begins his novel with nature rather than characters. One theme of Nostromo is that human action amounts to nothing more than a tiny bestirring in a vast and indifferent universe. This chapter, which passes through scenes of gigantic nature to zoom in on the little, half-glimpsed town, helps convey that pessimistic message.