The founder of the Dead Poets Society of America is halfway to his goal of visiting the gravesites of 500 bards. Walter Skold on Thursday is visiting the gravesite of Henry Wadsworth Longfellow’s brother Samuel at Portland’s Western Cemetery. Skold says Samuel Longfellow was a hymn writer, pastor and poet. It’ll be his 251st burial plot visit, marking the kickoff of events leading to Dead Poets Remembrance Day on Oct. 7. Skold, who’s from Freeport, Maine, pushed for a national holiday after he discovered that the graves of many of the nation’s literary forebears have been neglected. Highlights this year will include a tribute to the poetry of John Updike and a special midnight reading of “The Raven” at Poe Corner in Boston, Edgar Allan Poe’s hometown.