The income from his writings, though small, was sufficient for him to marry in 1844; and not long after this event he became a regular contributor to the _Anti-Slavery Standard_. In this appeared the first series of the _Biglow Papers_, in which, through vigorous prose and verse, largely in the Yankee dialect of Hosea Biglow, he protested against the evils that brought on the Mexican War. The collected numbers of the series were published in 1848 and shared the popularity of two other of Lowell's greatest works, produced in the same year,--the _Fable for Critics_ and _The Vision of Sir Launfal_, a beautiful narrative poem filled with the spirit of Christian brotherhood.
It was not long after this that Lowell began to feel that his work as a writer for the abolitionist cause was narrowing in its effect. For "red-hot" reform he had no liking. It seemed to him that the hope of his cause lay not so much in treating others harshly as in living according to the high principles that the reformers professed. "The longer I live," he wrote, "the more am I convinced that the world must be healed by degrees. I see why Jesus came eating meat and drinking wine and companying with publicans and sinners. He preached the highest doctrine, but he lived the life of other men.... Let us sow the best seed we have ... and convert other men by our crops, not by drubbing them with our hoes or putting them under our harrows." He decided, then, to take life in a more leisurely way and let the poetic power that he considered his best gift express itself freely.
In 1851, accompanied by his wife and his two children, Lowell visited Europe. The months spent abroad gave him much wished-for opportunities for study and observation, but they were darkened by the death of his son Walter. Close upon this sorrow came the death of Mrs. Lowell in the following year (1853), after the return of the family to Elmwood. From that time for many months the poet could find relief from his keen sense of loss only in his literary work, and in the companionship of his daughter Mabel, the only one of his four children who had lived.
Some lectures on the English poets given at the Lowell institute in 1854-55 found so much favor with the authorities at Harvard College that soon afterward he was appointed to succeed Longfellow as professor of foreign languages and literatures. After a period of study in Europe, he assumed charge of classes at Harvard in 1856, and for sixteen years continued in this work, bringing to it with most remarkable success all the warmth and sincerity and broad scope of his own interest in the subjects that he taught. Not many months afterward he was still further honored by being given the editorship of the newly founded _Atlantic Monthly_, a position that he held until 1861. The year 1857 was made memorable also by his marriage to Miss Frances Dunlap, a much-valued friend and the governess of his daughter. In 1864 he became joint editor of the _North American Review_, and in this magazine continued the second series of the _Biglow Papers_, begun in the _Atlantic Monthly_, the series in which is expressed his finest power as a poet-patriot. Of the same excellence is the famous _Commemoration Ode_ written for memorial ceremonies held at Harvard College in honor of the students who had fallen during the war. Among other contributions to these periodicals were numerous studies of poets and poetry--essays that rank among the best of their kind. Thus did Lowell prove himself to possess a rare combination of the powers of original composition and of criticism.