THE ballad, one of the oldest and most truly popular forms of English poetry, has never died. Printing only revivified it, and after the broadsheet came the literary ballad-Keats's ' Belle Dame Sana Merci ,' ' The Ancient Mariner,' ' John Gilpin ,' Kipling's ' Barrack-Room Ballads,' and the rest, of which Mr. Stobart and Miss Somerville will speak this afternoon.