While in Peru Augustus became interested in the causes of earthquakes. He was able to observe the 1868 Arica earthquake and he studied the resulting damage and interviewed people about what they experienced. During this time Le Plongeon began to speak out against abuses by Jesuit priests and the Catholic Church in Peru. He published two anti-Jesuit books, "La religion de Jesus comparada con las ensenanzas de la Iglesia" (1867), and "Los Jesuitas y el Peru" (1869).