When Voices of the Night, Longfellow’s first book of
 poems, came out in 1839, Poe reiterated his prediction. Writing in the February 1840 issue of Burton’s Gentleman’s Magazine, Poe conceded that Longfellow had “idiosyncratic excellences” and a “fitful (unsteady) imagination.”
 But he also insisted that these were insufficient to “the ultimate achievement of any well-founded monument
– any enduring reputation.  .  .  . [H]e appears to us singularly deficient in all those important faculties which give artistical power, and without which never was immortality effected.”

Boston Public Library, Rare Books & Manuscripts