Indignant over the expulsion of his colleagues, del Río showed solidarity by himself entering voluntary exile in Philadelphia for four years. There he was highly honored. He took part in the scientific activities of the American Philosophical Society (elected 1830) and was elected president of the Geological Society of Philadelphia. John Hurtel of Philadelphia published a new edition of del Rio's book in 1832. Del Rio returned to Mexico in 1834 and again occupied the chair of mineralogy at the college. He was also given the chair of geology.
