Chapter 15 Summary and Analysis

While anchored at Valparaiso, Darwin prepares to cross the Andes Mountains through the Portillo pass. Mariano Gonzales accompanies him and ten mules loaded down with extra supplies in case they become snowed in while crossing the mountains.

The rivers impress Darwin as being very fast and powerful, loosening and rolling rocks in the torrents. This action creates a distinctive clicking sound in the purple mountains. He reflects on the richness of mineral resources and how most mines are discovered by men who drive cattle into the mountains, simply by picking up stones and noticing the kinds of ore in them.

Views in the high and largely barren mountains are magnificent, but for Darwin's interest in plants and animals, almost no new species can be found. He speculates on how the geology develops on the mountain through snow melt percolating and loosening...