In 1845, 1846, and 1847 he wrote abundantly, widening his relations with the magazines of the day and apparently finding no trouble in marketing his wares. One piece of verse is preëminent in this period for both immediate and lasting appeal--"The Present Crisis." It was Lowell's way of protesting at the national policy in the war with Mexico and, in its contrast with Thoreau's method (see p. 224), throws light on the reformer's later strictures upon the recluse. It was repeated on every hand during the next twenty years and was given special emphasis through its frequent use by such orators as Wendell Phillips and Charles Sumner. It was in 1848, however, that he came to the fullness of his powers, contributing some forty articles to four Boston periodicals and publishing four books "Poems (Second Series)," "A Fable for Critics," "The Biglow Papers," and "The Vision of Sir Launfal." He was only ten years out of college, and at that was only twenty-nine years old, but he showed secure taste, confident judgment, and a seasoned ease of humor which belong to middle life. In the first and last, the more literary volumes, there is perhaps more evidence of youth. It appears in the effusive grief on the loss of his little daughter, and in "Sir Launfal" Lowell seems to be working too clearly after the somewhat confused formula laid down in the introduction to _The Pioneer_. Americans were to attempt a natural rather than a national literature. They were to remember that "new occasions teach new duties." "To be the exponent of a young spirit which shall aim at power through gentleness ... and in which freedom shall be attempered to love by a reverence for all beauty wherever it may exist, is our humble hope." So in order not to be too aggressively national, he derived a theme from the literature of chivalry and adorned it with a democratic, nineteenth-century moral.