In 1840 he gave up his pastoral duties to become a public lecturer and spend time on literary activities. In 1843-46, he was in England giving lectures on the Middle Ages, and on his return to the United States continued to lecture for many years in the principal towns and cities, giving over 6,000 lectures in all. In 1864, he received his LL.D. from the University of the City of New York. From 1866 to 1876, he was lecturer on history at Dartmouth College.