The subject of this article is a letter from Eduard Poeppig (1798-1868) addressed to Alexander von Humboldt (1769-1859), dated Leipzig on July 15, 1835; the writing is About the volcanoes in Chile. From a synoptic view of the scientific horizon of the time in terms of geology, it is possible to observe the world of personal relationships in which this epistolary episode takes place, also using other collections of the personal correspondence of explorers. Poeppig's essay is published in the Spanish version in the appendix.