In 1829, being urgently called to important services in connection with the American Education Society, to the regret of his people and with personal reluctance, he resigned his pastorate to enter upon these new duties; and, accordingly, was dismissed December 15, 1829, and removed to Boston, where he resided for some years. So important were his labors and so successful in this new field of effort, that January 25, 1832, he was chosen, with great enthusiasm, to succeed Dr. Cornelius to the secretaryship of the society, which office he filled with fidelity and acceptance until he resigned in 1841 to accept a professorship in Dartmouth College. In 1833, Mr. Cogswell received from Williams College the degree of Doctor of Divinity, and in 1837 was chosen one of the trustees of Andover Theological Seminary. He removed to Hanover, N. H., and entered upon his duties as professor of National Education and History in Dartmouth College. This position he resigned in 1844 to accept the presidency and professorship of Christian Theology in the Gilmanton Theological Seminary. Rev. Dr. Cogswell for many years had been engaged in editorial work, and was much interested in historical and genealogical researches. In 1846 he retired from his connection with the seminary, about to be discontinued, and gave himself exclusively to literary pursuits, except that he usually preached on the Sabbath. In the few remaining years of his life he performed a vast amount of literary labor, and became known very widely, and was honored with a membership in nearly all the historical societies in this country and in Europe. Rev. Dr. Cogswell published several works, viz.: a Catechism on the Doctrines and Duties of Religion; a Manual of Theology and Devotions; the Theological Class Book; the Christian Philanthropist; and Letters to Young Men Preparing for the Christian Ministry. All these works passed through several editions. His published editorial works were: Four vols. of the American Quarterly Register, 1837-1841; New Hampshire Repository, 2 vols.; the New England Historical and Genealogical Register, vol. I.; New Hampshire Historical Collections, vol. VI. He published, also, various miscellaneous writings. Rev. Dr. William and Joanna (Strong) Cogswell had four children. The eldest, a daughter, died in infancy. William Strong Cogswell was born in South Dedham, April 11, 1828, and died April 6, 1848, at the age of twenty years. He was a young man of rare ability and brilliant promise. At the time of his death he was a member of the senior class in Dartmouth College. Mary Joanna Cogswell was born June 6, 1832, in Boston, Mass. She graduated at Gilmanton Academy in 1851; married, September 20, 1858, Rev. E. O. Jameson, who is now (1882) pastor of the First Church of Christ, in Medway, Mass.