What to read after Political Essay on the Kingdom of New Spain?

The acclaimed Prussian naturalist Alexander von Humboldt (1769-1859) was referred to by Charles Darwin as 'the greatest scientific traveller who ever lived'. Several of his works were in the library aboard the Beagle, including the multi-volume Personal Narrative of Travels, two books on geology and Tableaux de la nature (all reissued in the Cambridge Library Collection). Darwin's copy of this two-volume 1811 New York edition of Humboldt's Political Essay (originally published in French earlier that year) is inscribed 'Buenos Ayres', suggesting he acquired it there in 1832-3, without its accompanying atlas (forthcoming). Humboldt had spent a year in Mexico in 1803-4, and was struck by its 'civilization' as compared to regions of South America that he had visited earlier on his expedition. The work begins with a 'geographical introduction', after which Humboldt describes Mexico's topography, agriculture, population, mines, industry and commerce, its economic state and its military defences.