Nineteen rare watercolors by William Blake were auctioned Tuesday in New York. “The works, illustrations for “The Grave,” a 1743 poem by the Scottish writer Robert Blair, were discovered five years ago by two British booksellers. At the time, experts heralded them as the most important Blake discovery in a century and said the illustrations should stay together. It appeared that the public agreed; some in the audience spoke of the breakup of the collection as a criminal procedure.”