The handwritten original first half of Mark Twain's "Huckleberry Finn" - differing considerably from the published version - has been found in an attic, a discovery hailed as an extraordinary literary find.

The 665-page manuscript, which Twain gave to a Buffalo, N.Y., library, had been lost for more than a century. Twain scholars hope to reunite it eventually with the second half, which has been at the library since the 1880s."Finding it is far beyond what anyone believed could have happened," said Robert H. Hirst, general editor of the Mark Twain Project at the University of California, Berkeley, where Twain's letters are kept.

The rough draft was found last fall by the granddaughter of the library curator to whom Twain originally presented it.

"The Adventures of Huckleberry Finn," published in 1884, is the tale of an incorrigible boy who escapes from "civilization" in a small Midwestern town and sets off on a series of adventures along the Mississippi River with a runaway slave named Jim.

Ernest Hemmingway called the book the wellspring of the modern American novel.

"If you had to think what would be the greatest American literary manuscript, this would be it," said Paul Needham, head of Sotheby's book and manuscript department in New York. Sotheby's analysts confirmed the text's authenticity.

With wide variations from the published text, and about 20 pages of narration by Jim that later were deleted altogether, the newly found manuscript promises to keep Twain experts busy revising theories and books for years to come.

Twain, whose real name was Samuel Langhorne Clemens, started "Huckleberry Finn" in 1876, worked on it a few years, then put it away, Hirst said. He returned to it in 1883 and published it the following year.

In November 1885, he received a request for the manuscript of his book "Life on the Mississippi" from James Fraser Gluck.

Gluck, a curator at what is now the Buffalo and Erie County Public Library, made clear in his letter that he wanted the manuscript for the library, not himself, Hirst said.

Twain instead volunteered the second half of "Huckleberry Finn," saying the first half had been lost by the printer.

Letters in the Berkeley collection show Twain found the first half in 1887 and sent it to the Buffalo library, which acknowledged its receipt.

But then it disappeared again and was widely believed lost forever.

Last fall, Gluck's granddaughter, a 62-year-old librarian, found the manuscript in a steamer trunk in her attic in Hollywood.